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In this paper, we define the Bartnik mass of a domain whose boundary is connected and compact, has scalar curvature bounded below −n(n − 1), and whose extensions are asymptotically hyperbolic manifolds. With this definition, we show that asymptotically hyperbolic admissible extensions of a domain that achieve the Bartnik mass must admit a static potential. Given a non-static admissible extension of a domain, we are able to construct a one-parameter family of metrics that are close to the original metric, have smaller mass, share the same bound on the scalar curvature, and contain the domain isometrically. [ABSTRACT FROM AUTHOR]

Absorption of radiation by solution is described by its frequency-dependent dielectric function and can be viewed as a specific application of the dielectric theory of solutions. For ideal solutions, the dielectric boundary-value problem separates the polar response into the polarization of the void in the liquid, created by the solute, and the response of the solute dipole. In the case of a protein as a solute, protein nuclear dynamics do not project on significant fluctuations of the dipole moment in the terahertz domain of frequencies and the protein dipole can be viewed as dynamically frozen. Absorption of radiation then reflects the interfacial polarization. Here we apply an analytical theory and computer simulations to absorption of radiation by an ideal solution of lysozyme. Comparison with the experiment shows that Maxwell electrostatics fails to describe the polarization of the proteinwater interface and the "Lorentz void," which does not anticipate polarization of the interface by the external field (no surface charges), better represents the data. An analytical theory for the slope of the solution absorption against the volume fraction of the solute is formulated in terms of the cavity field response function. It is calculated from molecular dynamics simulations in good agreement with the experiment. The protein hydration shell emerges as a separate sub-ensemble, which, collectively, is not described by the standard electrostatics of dielectrics. [ABSTRACT FROM AUTHOR]

We have studied the limits of stability in the first order liquid-solid phase transition in a Lennard- Jones system by means of the short-time relaxation method and using the bond-orientational order parameter Q6. These limits are compared with the melting line. We have paid special attention to the supercooled liquid, comparing our results with the point where the free energy cost of forming a nucleating droplet goes to zero. We also indirectly estimate the dimension associated to the critical nucleus at the spinodal, expected to be fractal according to mean field theories of nucleation. [ABSTRACT FROM AUTHOR]

Cross-membrane electron transport between cofactors localized in proteins of mitochondrial respiration and bacterial photosynthesis is the source of all biological energy. The statistics and dynamics of nuclear fluctuations in these protein/membrane/water heterogeneous systems are critical for their energetic efficiency. The results of 13 μs of atomistic molecular dynamics simulations of the membrane-bound bc1 bacterial complex are analyzed here. The reaction is affected by a broad spectrum of nuclear modes, with the slowest dynamics in the range of time-scales ~0.1-1.6 μs contributing half of the reaction reorganization energy. Two reorganization energies are required to describe protein electron transfer due to dynamical arrest of protein conformations on the observation window. This mechanistic distinction allows significant lowering of activation barriers for reactions in proteins. [ABSTRACT FROM AUTHOR]

Water interfacing hydrated proteins carry properties distinct from those of the bulk and is often described as a separate entity, a "biological water." We address here the question of which dynamical and structural properties of hydration water deserve this distinction. The study focuses on different aspects of the density and orientational fluctuations of hydration water and the ability to separate them experimentally by combining depolarized light scattering with dielectric spectroscopy. We show that the dynamics of the density fluctuations of the hydration shells reflect the coupled dynamics of the solute and solvent and do not require a special distinction as "biological water." The orientations of shell water molecules carry dramatically different physics and do require a separation into a sub-ensemble. Depending on the property considered, the perturbation of water's orientational structure induced by the protein propagates 3-5 hydration shells into the bulk at normal temperature. [ABSTRACT FROM AUTHOR]

The density and orientational relaxation of bulk water can be separately studied by depolarized light scattering (DLS) and dielectric spectroscopy (DS), respectively. Here, we ask the question of what are the leading collective modes responsible for polarization anisotropy relaxation (DLS) and dipole moment relaxation (DS) of solutions involving mostly hydrophobic solute-water interfaces. We study, by atomistic molecular dynamics simulations, the dynamics and structure of hydration water interfacing N-Acetyl-leucine-methylamide dipeptide. The DLS response of the solution is consistent with three relaxation processes: bulk water, rotations of single solutes, and collective dipole-induceddipole polarizability of the solutes, with the time-scale of 130-200 ps. No separate DLS response of the hydration shell has been identified by our simulations. Density fluctuations of the hydration layer, which largely contribute to the response, do not produce a dynamical process distinct from bulk water. We find that the structural perturbation of the orientational distribution of hydration waters by the dipeptide solute is quite significant and propagates ~3-5 hydration layers into the bulk. This perturbation is still below that produced by hydrated globular proteins. Despite this structural perturbation, there is little change in the orientational dynamics of the hydration layers, compared to the bulk, as probed by both single-particle orientational dynamics and collective dynamics of the dipole moment of the shells. There is a clear distinction between the perturbation of the interfacial structure by the solute-solvent interaction potential and the perturbation of the interfacial dynamics by the corresponding forces. [ABSTRACT FROM AUTHOR]

Electric field produced inside a solute by a uniformly polarized liquid is strongly affected by dipolar polarization of the liquid at the interface. We show, by numerical simulations, that the electric 'cavity' field inside a hydrated non-polar solute does not follow the predictions of standard Maxwell's electrostatics of dielectrics. Instead, the field inside the solute tends, with increasing solute size, to the limit predicted by the Lorentz virtual cavity. The standard paradigm fails because of its reliance on the surface charge density at the dielectric interface determined by the boundary conditions of the Maxwell dielectric. The interface of a polar liquid instead carries a preferential in-plane orientation of the surface dipoles thus producing virtually no surface charge. The resulting boundary conditions for electrostatic problems differ from the traditional recipes, affecting the microscopic and macroscopic fields based on them. We show that relatively small differences in cavity fields propagate into significant differences in the dielectric constant of an ideal mixture. The slope of the dielectric increment of the mixture versus the solute concentration depends strongly on which polarization scenario at the interface is realized. A much steeper slope found in the case of Lorentz interfacial polarization also implies a higher free energy penalty for polarizing such mixtures. [ABSTRACT FROM AUTHOR]

We present the results of an analytical theory and numerical simulations of microscopic fields in dipolar liquids. Fields within empty spherical cavities (cavity field) and within cavities with a probe dipole (directing field) and the field induced by a probe dipole in the surrounding liquid (reaction field) are considered. Instead of demanding the field produced by a liquid dielectric in a large-scale cavity to coincide with the field of Maxwell’s dielectric, we continuously increase the cavity size to reach the limit of a mesoscopic dimension and establish the continuum limit from the bottom up. Both simulations and analytical theory suggest that the commonly applied Onsager formula for the reaction field is approached from below, with increasing cavity size, by the microscopic solution. On the contrary, the cavity and directing fields do not converge to the limit of Maxwell’s dielectric. The origin of the disagreement between the standard electrostatics and the results obtained from microscopic models is traced back to the failure of the former to account properly for the transverse correlations between dipoles in molecular liquids. A new continuum equation is derived for the cavity field and supported by numerical simulations. Experimental tests of the theoretical results are suggested. [ABSTRACT FROM AUTHOR]

Frequency modulation and harmonic detection are extensively employed in a variety of experimental techniques and offer a detection sensitivity limited only by quantum noise. We discuss a simple experiment using wavelength modulation spectroscopy and near infrared diode lasers operating in the 780 nm region to detect rubidium hyperfine spectra. Modulation spectroscopy techniques are employed to improve the signal to noise ratio for the detection of weak signals and thus significantly improve the sensitivity and specificity for detection. By using quantum cascade lasers and wavelength modulation spectroscopy, one can detect trace species at sub-ppm level, which has numerous applications in diverse areas such as medical diagnostics, food processing, industrial applications, and environmental monitoring. [ABSTRACT FROM AUTHOR]

R. Bruce Lindsay, reknowned physicist, administrator, educator, and editor, is remembered by his friends and colleagues. [ABSTRACT FROM AUTHOR]

Sound is more than an ''oscillation...in a medium'' or ''an auditory sensation evoked by the oscillation.'' From an academic standpoint it involves physical sciences, engineering, life sciences, and art. From an application standpoint it is also related to invention, design, economics, business, and even legislation. These relationships can be described and diagrammed in several different ways. The field of musical acoustics is used as an example of the interaction among the various disciplines. © 1996 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Causes for the decrease in rate of piano tone decay with time of tone duration were investigated, including the following: different rates for different vibration modes or groups of modes, nonlinear transformation of mechanical energy to acoustical energy, storage of mechanical energy for subsequent acoustical radiation, transfer of energy between string modes perpendicular and parallel to the bridge, interference among strings that are almost exactly in tune, and change in rate of energy transfer from the multiple-string source to the bridge during the transition from an initial in-phase condition to a later out-of-phase condition. The last two closely related factors were found to control the rate change in most cases. [ABSTRACT FROM AUTHOR]

The acoustical effects achieved and the techniques used in the radiation of organ tone are quite different from the conventional effects and practices of public-address sound systems. For the latter, point-source radiation with high uniform directivity and a minimum of reverberation are sought, in general, for the creation of the illusion of 'presence' of the original sound source. However in organ music the sound sources and their images are widely distributed in space. This is especially true in those typical cases where the tone sources are enclosed in an organ chamber, or are installed in a highly reverberant environment. Another distinctive feature of organ tone radiation systems is the relative importance of the octave below 60 cps. This paper contains design principles for electronic organ tone chambers and describes several types of organ tone cabinets now in use. Examples of the application of organ installation principles are given. [ABSTRACT FROM AUTHOR]

Simple procedures are given for the subjective measurement of earphone response by two methods. The first method, which is rather widely recognized, requires the subject to match the loudness of an earphone tone to the loudness of a free-field reference tone of the same frequency. Interpretation of the data from this method is direct, but the facilities, technique and time required are considerable. A second method, less widely used, involves the loudness balancing of an earphone tone of variable frequency to that of an earphone reference tone of fixed frequency and level. This method is much simpler, and can be used to measure earphone response under circumstances where the first method is virtually impossible. However, the interpretation of the data is less direct. This paper is an analysis of the two methods which attempts to develop a correspondence between the data obtained by the two methods. [ABSTRACT FROM AUTHOR]

A graphical function W(r, c) has been determined experimentally, in which W is word articulation, r is the relative level of unclipped speech and the noise, and c is the amount of uniform, symmetrical, speech-peak clipping. Pre-emphasis of the speech signal gave an approximately uniform speech spectrum prior to clipping. Uniform, random noise was mixed with the clipped speech before postequalization, making the final noise spectrum similar in shape to the speech spectrum. The real-ear response of the earphones was compensated electrically to yield a uniform orthotelephonic response for the communication system, in the frequency range contributing significantly to articulation index. For constant clipping cn the function W(r, cn) approaches W(r, 0) as a limit for sufficiently large values of r. For c

Decay curves were recorded for an upright piano, a baby grand, and an electronic spinet. For some tones the partials were recorded separately. Decay rates for the electronic piano were measured at different levels of piano amplification. Analysis of the data reveals the degree of control exerted by the sounding board upon decay rate, particularly in the initial stage of decay. The significance of this control by the sounding board is discussed, in relation to the problem of electrical amplification of piano tones. [ABSTRACT FROM AUTHOR]

An analysis is made of the problem of intelligence pick-up from anatomical vibration. Methods for measuring the actual and effective response-frequency characteristics of the throat are described. Measurements on the variation of effective response among different subjects are discussed in connection with the concept of 'oral efficiency.' Design and performance data are given for several magnetic throat microphones of relatively high sensitivity. [ABSTRACT FROM AUTHOR]

Methods of acoustical measurement and of data presentation are reviewed, with emphasis on relating headphone data to the requirements of the communications and monitoring fields of application. Data are shown to demonstrate the importance of statistical analyses of the performance of headphones on different wearers. Some effects of presenting too 'artificial' an acoustical load to the receiver during measurement are illustrated. An experiment in artificial ear development is described. The requirements for an improved artificial ear are outlined, based in part upon the experimental work. [ABSTRACT FROM AUTHOR]

Elastic network models coarse grain proteins into a network of residue beads connected by springs. We add dissipative dynamics to this mechanical system by applying overdamped Langevin equations of motion to normal-mode vibrations of the network. In addition, the network is made heterogeneous and softened at the protein surface by accounting for hydration of the ionized residues. Solvation changes the network Hessian in two ways. Diagonal solvation terms soften the spring constants and off-diagonal dipole-dipole terms correlate displacements of the ionized residues. The model is used to formulate the response functions of the electrostatic potential and electric field appearing in theories of redox reactions and spectroscopy. We also formulate the dielectric response of the protein and find that solvation of the surface ionized residues leads to a slow relaxation peak in the dielectric loss spectrum, about two orders of magnitude slower than the main peak of protein relaxation. Finally, the solvated network is used to formulate the allosteric response of the protein to ion binding. The global thermodynamics of ion binding is not strongly affected by the network solvation, but it dramatically enhances conformational changes in response to placing a charge at the active site of the protein. [ABSTRACT FROM AUTHOR]

Organ music produced in small rooms having little natural reverberation can be enhanced by the addition of artificial reverberation. A direct method of adding the aftersound at the electroacoustic transducer itself is described. This is in contrast to the more conventional reverberation systems employing driving transducers, time-delay means, pickup transducers, and mixing and amplifying circuits. Multiply resonant helical mechanical delay lines store the energy and radiate it at a later time. In one model the coupling to the transducer is mechanical, and in the other model acoustical coupling provides a number of practical and acoustical advantages. [ABSTRACT FROM AUTHOR]

A supplementary sound system was one of the technical innovations of the 1961 summer season of grand opera at the Cincinnati Zoo Pavilion, a covered but unenclosed area seating 2500 people. Neither the 85-piece orchestra nor the Metropolitan and European soloists and the chorus required or were provided sound re-enforcement. The versatile, flexible sound-amplification and reproduction system was intended and used instead for a variety of supplementary purposes as follows: (a) auditory relocation of individual instruments or groups from the orchestra pit (actual) to backstage or on-stage (apparent) positions, to fulfill dramatic requirements; (b) solo voice modification and motion, when 'supernatural' timbre or spatial effects were appropriate; (c) sound effects which were difficult for the orchestra percussionists to produce as realistically or dramatically as desired; (d) electronic musical instruments. Microphones in the orchestra pit and backstage, stereo tape playback, and a Baldwin electronic organ were the program sources. Sound effects filters, artificial reverberation, and a Choratone (for organ) were available for modification effects. In addition to patch panel interconnection, a keyboard of variable resistance switches provided rapid, smooth transitions among the seven amplification channels leading to different loudspeaker locations (e.g., backstage, on stage, proscenium, ceiling, and rear). [ABSTRACT FROM AUTHOR]

The acoustical radiation from trumpets, Flugelhorns, trombones, and French and baritone horns has been greatly attentuated, without the adverse effects that conventional mutes have upon the natural timbre of the tone and the acoustical impedance at the player's lips. The new lightweight attenuators [Patent 3,555,956] are mounted upon the horns in contrast to a previous type [Patent 2,618,191] demonstrated at a Society meeting in 1947 by the present senior author. The absorptive part of the attenuator and the enclosed microphone lie just outside the open-end reflection region of the horn mouth, minimizing reaction upon the resonant horn and its modal frequencies. Listening to the enclosed microphone by earphones allows a performer to practice in relative privacy. A classroom of brass students so equipped can be taught individually, in groups or in ensembles by one teacher through a versatile communication system. [ABSTRACT FROM AUTHOR]

An inventor for 23 U.S. patents, assigned to Submarine Signal Company and Raytheon Company, Batchelder contributed numerous inventive concepts to underwater sound transducers and arrays, and to systems for hunting, detection, and ranging. For 41 years he regularly reviewed for the Journal a total of 3035 patents on transducers, systems, and measuring devices, mostly in underwater sound, and contributed his last review only a month before his death. Examples from his patents and from his insightful reviews will be shown. [ABSTRACT FROM AUTHOR]