Essential nonlinearities in hearing

Our hearing organ, the cochlea, evidently poises itself at a Hopf bifurcation to maximize tuning and amplification. We show that in this condition several effects are expected to be generic: compression of the dynamic range, infinitely shrap tuning at zero input, and generation of combination tones. These effects are "essentially" nonlinear in that they become more marked the smaller the forcing: there is no audible sound soft enough not to evoke them. All the well-documented nonlinear aspects of hearing therefore appear to be consequences of the same underlying mechanism.Comment: 4 pages, 3 figure

Hair Cell Bundles: Flexoelectric Motors of the Inner Ear

Microvilli (stereocilia) projecting from the apex of hair cells in the inner ear are actively motile structures that feed energy into the vibration of the inner ear and enhance sensitivity to sound. The biophysical mechanism underlying the hair bundle motor is unknown. In this study, we examined a membrane flexoelectric origin for active movements in stereocilia and conclude that it is likely to be an important contributor to mechanical power output by hair bundles. We formulated a realistic biophysical model of stereocilia incorporating stereocilia dimensions, the known flexoelectric coefficient of lipid membranes, mechanical compliance, and fluid drag. Electrical power enters the stereocilia through displacement sensitive ion channels and, due to the small diameter of stereocilia, is converted to useful mechanical power output by flexoelectricity. This motor augments molecular motors associated with the mechanosensitive apparatus itself that have been described previously. The model reveals stereocilia to be highly efficient and fast flexoelectric motors that capture the energy in the extracellular electro-chemical potential of the inner ear to generate mechanical power output. The power analysis provides an explanation for the correlation between stereocilia height and the tonotopic organization of hearing organs. Further, results suggest that flexoelectricity may be essential to the exquisite sensitivity and frequency selectivity of non-mammalian hearing organs at high auditory frequencies, and may contribute to the “cochlear amplifier” in mammals

Clustering patterns of physical activity, sedentary and dietary behavior among European adolescents: The HELENA study

<p>Abstract</p> <p>Background</p> <p>Evidence suggests possible synergetic effects of multiple lifestyle behaviors on health risks like obesity and other health outcomes. A better insight in the clustering of those behaviors, could help to identify groups who are at risk in developing chronic diseases. This study examines the prevalence and clustering of physical activity, sedentary and dietary patterns among European adolescents and investigates if the identified clusters could be characterized by socio-demographic factors.</p> <p>Methods</p> <p>The study comprised a total of 2084 adolescents (45.6% male), from eight European cities participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study. Physical activity and sedentary behavior were measured using self-reported questionnaires and diet quality was assessed based on dietary recall. Based on the results of those three indices, cluster analyses were performed. To identify gender differences and associations with socio-demographic variables, chi-square tests were executed.</p> <p>Results</p> <p>Five stable and meaningful clusters were found. Only 18% of the adolescents showed healthy and 21% unhealthy scores on all three included indices. Males were highly presented in the cluster with high levels of moderate to vigorous physical activity (MVPA) and low quality diets. The clusters with low levels of MVPA and high quality diets comprised more female adolescents. Adolescents with low educated parents had diets of lower quality and spent more time in sedentary activities. In addition, the clusters with high levels of MVPA comprised more adolescents of the younger age category.</p> <p>Conclusion</p> <p>In order to develop effective primary prevention strategies, it would be important to consider multiple health indices when identifying high risk groups.</p

NACA Technical Notes

Report presenting a study of accurate values of the specific heat for dry air applied to the calculation of work required to compress dry air. Two charts are provided that allow the work of compression to be determined from the initial temperature, overall pressure ratio, and either the compression exponent or adiabatic efficiency of the compressor

Risk factors for adverse drug events among nursing home residents.

BACKGROUND: In a prospective study of nursing home residents, we found adverse drug events (ADEs) to be common, serious, and often preventable. To direct prevention efforts at high-risk residents, information is needed on resident-level risk factors. METHODS: Case-control study nested within a prospective study of ADEs among residents in 18 nursing homes. For each ADE, we randomly selected a control from the same home. Data were abstracted from medical records on functional status, medical conditions, and medication use. RESULTS: Adverse drug events were identified in 410 nursing home residents. Independent risk factors included being a new resident (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.5-5.2) and taking anti-infective medications (OR, 4.0; CI, 2.5-6.2), antipsychotics (OR, 3.2; CI, 2.1-4.9), or antidepressants (OR, 1.5; CI, 1.1-2.3). The number of regularly scheduled medications was associated with increased risk of ADEs; the OR associated with taking 5 to 6 medications was 2.0 (CI, 1.2-3.2); 7 to 8 medications, 2.8 (CI, 1.7-4.7); and 9 or more, 3.3 (CI, 1.9-5.6). Taking supplements or nutrients was associated with lower risk (OR, 0.42; CI, 0.27-0.63). Preventable ADEs occurred in 226 residents. Independent risk factors included taking opioid medications (OR, 6.6; CI, 2.3-19.3), antipsychotics (OR, 4.0; CI, 2.2-7.3), anti-infectives (OR, 3.0; CI, 1.6-5.8), antiepileptics (OR, 2.2; CI, 1.1-4.5), or antidepressants (OR, 2.0; CI, 1.1-3.5). Scores of 5 or higher on the Charlson Comorbidity Index were associated with increased risk of ADEs (OR, 2.6; CI, 1.1-6.0). The number of regularly scheduled medications was also a risk factor: the OR for 7 to 8 medications was 3.2 (CI, 1.4-6.9) and for 9 or more, 2.9 (CI, 1.3-6.8). Residents taking nutrients or supplements were at lower risk (OR, 0.27; CI, 0.14-0.50). CONCLUSIONS: It is possible to identify nursing home residents at high risk of having an ADE. Particular attention should be directed at new residents, those with multiple medical conditions, those taking multiple medications, and those taking psychoactive medications, opioids, or anti-infective drugs

Incidence and preventability of adverse drug events in nursing homes.

PURPOSE: Adverse drug events, especially those that may have been preventable, are among the most serious concerns about medication use in nursing homes. We studied the incidence and preventability of adverse drug events and potential adverse drug events in nursing homes.METHODS: We performed a cohort study of all long-term care residents of 18 community-based nursing homes in Massachusetts during a 12-month observation period. Potential drug-related incidents were detected by stimulated self-report by nursing home staff and by periodic review of the records of nursing home residents by trained nurse and pharmacist investigators. Each incident was classified by 2 independent physician-reviewers, using a structured implicit review process, by whether or not it constituted an adverse drug event or potential adverse drug event (those that may have caused harm, but did not because of chance or because they were detected), by the severity of the event (significant, serious, life-threatening, or fatal), and by whether it was preventable. Examples of significant events included nonurticarial rashes, falls without associated fracture, hemorrhage not requiring transfusion or hospitalization, and oversedation; examples of serious events included urticaria, falls with fracture, hemorrhage requiring transfusion or hospitalization, and delirium. RESULTS: During 28,839 nursing home resident-months of observation in the 18 participating nursing homes, 546 adverse drug events (1.89 per 100 resident-months) and 188 potential adverse drug events (0.65 per 100 resident-months) were identified. Of the adverse drug events, 1 was fatal, 31 (6%) were life-threatening, 206 (38%) were serious, and 308 (56%) were significant. Overall, 51% of the adverse drug events were judged to be preventable, including 171 (72%) of the 238 fatal, life-threatening, or serious events and 105 (34%) of the 308 significant events (P \u3c 0.001). Errors resulting in preventable adverse drug events occurred most often at the stages of ordering and monitoring; errors in transcription, dispensing, and administration were less commonly identified. Psychoactive medications (antipsychotics, antidepressants, and sedatives/hypnotics) and anticoagulants were the most common medications associated with preventable adverse drug events. Neuropsychiatric events were the most common types of preventable adverse drug events.CONCLUSIONS: Adverse drug events are common and often preventable in nursing homes. More serious adverse drug events are more likely to be preventable. Prevention strategies should target the ordering and monitoring stages of pharmaceutical care