Modeling the Intelligibility Benefit of Active Noise Cancelation in Hearing Devices That Improve Signal-to-Noise Ratio.

The extent to which active noise cancelation (ANC), when combined with hearing assistance, can improve speech intelligibility in noise is not well understood. One possible source of benefit is ANC's ability to reduce the sound level of the direct (i.e.

A spectroscopic method to estimate the binding potency of amphiphile assemblies.

A fast and convenient spectroscopic methodology to determine the water uptake capacity of amphiphile assemblies studied in multilayer films is presented. This method was developed to provide a reliable but relatively simple tool for estimating the binding potency of such complex systems. The water-binding potency represents a general propensity of higher-order systems to bind or embed relevant ligands, such as various non-lipid effectors in the case of artificial lipid membranes.

Results of the National Institute for Occupational Safety and Health-U.S. Environmental Protection Agency interlaboratory comparison of American National Standards Institute S12.6-1997 Methods A and B.

The National Institute for Occupational Safety and Health and the Environmental Protection Agency sponsored the completion of an interlaboratory study to compare two fitting protocols specified by ANSI S12.6-1997 (R2002) [(2002). American National Standard Methods for the Measuring Real-Ear Attenuation of Hearing Protectors, American National Standards Institute, New York].

Hydration-induced changes of structure and vibrational frequencies of methylphosphocholine studied as a model of biomembrane lipids.

The chemical characteristics of the polar parts of phospholipids as the main components of biological membranes were investigated by using infrared (IR) spectroscopy and theoretical calculations with water as a probe molecule. The logical key molecule used in this study is methylphosphocholine (MePC) as it is not only a representative model for a polar lipid headgroup but itself has biological significance. Isolated MePC forms a compact (folded) structure which is essentially stabilized by two intramolecular C-H.

The influence of anisotropic membrane inclusions on curvature elastic properties of lipid membranes.

A membrane inclusion can be defined as a complex of protein or peptide and the surrounding significantly distorted lipids. We suggest a theoretical model that allows for the estimation of the influence of membrane inclusions on the curvature elastic properties of lipid membranes. Our treatment includes anisotropic inclusions whose energetics depends on their in-plane orientation within the membrane.

Amphiphile-induced tubular budding of the bilayer membrane.

Amphiphile-induced tubular budding of the erythrocyte membrane was studied using transmission electron microscopy. No chiral patterns of the intramembraneous particles were found, either on the cylindrical buds, or on the tubular nanoexovesicles. In agreement with these observations, the tubular budding may be explained by in-plane ordering of anisotropic membrane inclusions in the buds where the difference between the principal membrane curvatures is very large.

Effect of electronic ANR and conventional hearing protectors on vehicle backup alarm detection in noise.

An experiment was conducted wherein masked thresholds (using ascending method of limits) for a backup alarm were obtained in pink and red noise at 85 and 100 dBA for 12 participants immersed in a probability monitoring task and wearing a conventional passive hearing protection device (HPD, an earmuff or a foam earplug), an active noise reduction (ANR) headset, or no HPD at all (only in 85 dBA noise). Results revealed statistically significant between-HPD differences in red noise (from 2.3 to 3.

Lipid hydration: headgroup CH moieties are involved in water binding.

To explore the interaction potential of phospholipids, we have studied the hydration of diacyl phosphatidylcholine (PC) and methylphosphocholine (MePC), a pertinent model compound, by ir spectroscopy. Related ab initio Hartree-Fock calculations were performed for MePC. Water is considered ideal as a relevant probe molecule.

Hearing protection: surpassing the limits to attenuation imposed by the bone-conduction pathways.

With louder and louder weapon systems being developed and military personnel being exposed to steady noise levels approaching and sometimes exceeding 150 dB, a growing interest in greater amounts of hearing protection is evident. When the need for communications is included in the equation, the situation is even more extreme. New initiatives are underway to design improved hearing protection, including active noise reduction (ANR) earplugs and perhaps even active cancellation of head-borne vibration.

Hydration of biological molecules: lipids versus nucleic acids.

We used FTIR spectroscopy to comparatively study the hydration of films prepared from nucleic acids (DNA and double-stranded RNA) and lipids (phosphatidylcholines and phosphatidylethanolamines chosen as the most abundant ones) at room temperature by varying the ambient relative humidity in terms of solvent-induced structural changes. The nucleic acids and phospholipids both display examples of polymorphism on the one hand and structural conservatism on the other; even closely related representatives behave differently in this respect. DNA undergoes a hydration-driven A-B conformational transition, but RNA maintains an A-like structure independently of the water activity.

Lyotropic phase transitions in phospholipids as evidenced by small-angle synchrotron X-ray scattering.

Hydration is an important factor in regulating the phase behaviour of lipids and besides affects their interactions with other compounds relevant for biological membranes. We present a reliable and fast method to detect and characterise hydration-induced phase transitions in phospholipids by means of small-angle synchrotron X-ray scattering. Films consisting of aggregations of representatives of the two important lipid classes lecithins (DPPC a, POPC and OPPC,a for abbreviations, see below) and cephalins (DPPE and DOPE) were investigated at room temperature in dependence on relative humidity.

Cardiac injury during valve replacement surgery.

The commonly referenced mortality of cardiac valve replacement surgery is 2 to 5%. Some of this mortality is due to therapeutic misadventure during the procedure. Therapeutic misadventure during cardiac valve replacement may result in patterned injury of the heart, so that postmortem examination can establish the nature of the surgical injury.

Monoamine oxidase activity in rat erythrocytes: evidence for its localization in reticulocyte mitrochondria.

During growth of young rats, monoamine oxidase activity in erythrocyte membrane preparations decreases more rapidly than reticulocyte concentrations in the respective blood samples. Since reticulocytes lose their mitochondria prior to the substantia reticulo-filamentosa, the non-linear correlation between monoamine oxidase activity and reticulocyte counts indicates that erythrocyte monoamine oxidase is located in reticulocyte mitochondria.

Cyclic AMP-dependent protein kinases and binding sites for cyclic AMP in rat erythrocytes.

In red cell preparations from reticulocyte-poor (untreated animals; approximately 2% reticulocytes) and reticulocyte-rich blood (animals pretreated with acetylphenylhydrazide; approximately 60% reticulocytes) of rats, cAMP binding sites and cAMP-dependent protein kinase activities were determined. High affinity binding sites for cAMP were present both in membrane and cytoplasmic preparations; while the apparent binding constants determined in both cell fractions (approximately 3 x 10(-9) M for membrane, approximately 2 x 10(-8) M for cytoplasmic fractions) were independent of the reticulocyte content of the preparations, the respective numbers of sites were about twice as high in the reticulocyte-rich as in the reticulocyte-poor preparations. In membrane preparations, significant cAMP-dependent protein kinase activity could be detected only in membrane fractions from reticulocyte-rich blood which were considerably contaminated by intracellular components ("haemoglobin-containing membranes') while in washed ("haemoglobin-free') membranes no cAMP-dependent protein kinase activity was found.

The beta-adrenergic receptor-adenyl-cyclase system of rat reticulocytes: effects of adrenergic stimulants and inhibitors.

Non-nucleated red blood cells from rats contain adenyl cyclase, the activity of which is predominantly localized in the reticulocytes. Basal enzyme activities in membrane preparations from reticulocyte-rich blood (pretreatment of rats with acetyl-phenylhydrazide: about 60% reticuloytes) are about 5 times higher than in preparations from reticulocyte-poor blood (untreated animals: 2-3% reticulocytes). The enzyme activities are stimulated 10-fold by sodium fluoride (10(-2)M) and 6 to 8-fold by isoprenaline (10(-4)M).