Instrumental Window Research Articles

Time-domain simulation of a recorder using the model of a jet allowed to deflect overall

A sound production model of the flute-like instrument which allows the jet to deflect overall has been proposed recently. The overall deflection is introduced to satisfy flow consistency at the instrument's window (embouchure hole or mouth), i.e., the condition that the volume velocity swept by the oscillating jet should be equal to that through the window. The full oscillation of the jet is the sum of the deflection and the oscillation caused by fluid dynamical sinuous instability. This model can correctly reproduce the reflection function of a recorder's head as seen from the resonator. The next question is whether the model can predict the sound level of the flute-like instrument correctly. To answer the question, the model was first formulated in the time domain. In this formulation, measures were taken to prevent the oscillation from drifting. Using the time-domain model, physical modeling simulation of a recorder was performed to obtain sound levels produced for various blowing pressures. Artificial blowing experiments with a real instrument are in progress to compare the simulation results with the actual sound levels.

Jet oscillation model for flute-like instruments allowing overall deflection

A new jet oscillation model for flute-like instruments is proposed. This is based on a conventional semi-empirical model for a jet in half space disturbed by an acoustic cross flow. The proposed model, however, allows a jet to deflect and to oscillate as a whole with no phase delay in response to the volume flow through the instrument's window (embouchure hole or mouth). The overall jet deflection is essential to match the volume flow swept by the lateral motion of the jet to that through the window. The complete jet oscillation is the sum of the overall oscillation and that caused by fluid dynamical sinuous instability. The latter grows exponentially with a phase delay as the jet travels. The amplitude of acoustic volume velocity triggering this oscillation is much smaller than that through the window because most of it has already contributed to the overall deflection. The proposed model reasonably reproduces the recorder's head reflection coefficient measured in [Price et al., J. Acoust. Soc. Am. 138(5), 3282–3292 (2015)]. Synthesis of recorder sounds using this model is underway.

Fused silica as an anti-fouling material for oil sands optical instruments

Optical instruments have application in many chemical industries for use in inline observation, measurement, and process control for product and waste streams. Typically, these instruments are fitted with sapphire windows which offer extreme hardness, optical transparency and inertness but can be susceptible to fouling with hydrocarbons in the streams. This work explored the potential of fused silica as an alternative anti-fouling material for optical instrument windows for use in aqueous streams containing hydrocarbons. The advantage of fused silica is that it offers adequate hardness and transparency while retaining chemically reactive silanol groups on its surface. Closed loop experiments conducted with oil sands mature fine tailings (MFT) containing residual bitumen, a hydrocarbon known to cause severe fouling of optical windows, demonstrated no fouling issue on fused silica. The hydrophilicity of the optical surface increased following exposure to the mildly alkaline MFT. We hypothesized that in alkaline aqueous streams the silanol groups are deprotonated to create a negatively charged surface, thereby introducing a repulsive force between the surface and the negatively charged hydrocarbon droplets and increasing the hydrophilicity of both materials. Contrarily, the relatively inert sapphire is limited in its capacity to form negative surface charges and consistently fouled with bitumen. When silanol groups on the fused silica were removed via fluoro-functionalization, it resulted in complete fouling of the optical surface. Finally, bitumen fouling was observed on both fused silica and sapphire surfaces in neutral aqueous environments compared to none on the fused silica in an alkaline environment.

Fabrication of polydimethylsiloxane-attached solid slippery surface with high underwater transparency towards the antifouling of optical window for marine instruments

Marine optical instruments are commonly suffering serious biofouling problem caused by the adhesion of marine microorganisms, which severely affects the instruments to monitor the marine environment. Herein, we developed a robust solid slippery surface (SSS) by fabricated a covalently attached polydimethylsiloxane (PDMS) layer on glass substrate to solve the biofouling problem of marine optical instrument windows. The SSS could effectively inhibit the settlements of marine microorganism (bacteria and alga) in various environmental conditions, resulting from the high flexibility of PDMS molecular chains, and thus could maintain its high underwater-transparency. The antifouling mechanism of SSS was results from the weak nonspecific electrostatic Lifshitz-van der Waals forces and less specific hydrogen bonds between SSS and microorganism, which was been confirmed via both single bacterial force spectroscopy measurement and molecular dynamics simulation. Compared with the traditional slippery lubricant-infused porous surface (SLIPS), the SSS exhibited a better robust mechanical stability than that of the SLIPS. In addition, our study provides a valuable method to fabricated the SSS with reliable underwater-transmittance and antifouling properties, which is promised for the applications for the antifouling of marine optical instruments.

Dynamical and orientational structural crossovers in low-temperature glycerol.

Mean-square displacements of hydrogen atoms in glass-forming materials and proteins, as reported by incoherent elastic neutron scattering, show kinks in their temperature dependence. This crossover, known as the dynamical transition, connects two approximately linear regimes. It is often assigned to the dynamical freezing of subsets of molecular modes at the point of equality between their corresponding relaxation times and the instrumental observation window. The origin of the dynamical transition in glass-forming glycerol is studied here by extensive molecular dynamics simulations. We find the dynamical transition to occur for both the center-of-mass translations and the molecular rotations at the same temperature, insensitive to changes of the observation window. Both the translational and rotational dynamics of glycerol show a dynamic crossover from the structural to a secondary relaxation at the temperature of the dynamical transition. A significant and discontinuous increase in the orientational Kirkwood factor and in the dielectric constant is observed in the same range of temperatures. No indication is found of a true thermodynamic transition to an ordered low-temperature phase. We therefore suggest that all observed crossovers are dynamic in character. The increase in the dielectric constant is related to the dynamic freezing of dipolar domains on the time scale of simulations.

A generalized mean-squared displacement from inelastic fixed window scans of incoherent neutron scattering as a model-free indicator of anomalous diffusion confinement

Elastic fixed window scans of incoherent neutron scattering are an established and frequently employed method to study dynamical changes, usually over a broad temperature range or during a process such as a conformational change in the sample. In particular, the apparent mean-squared displacement can be extracted via a model-free analysis based on a solid physical interpretation as an effective amplitude of molecular motions. Here, we provide a new account of elastic and inelastic fixed window scans, defining a generalized mean-squared displacement for all fixed energy transfers. We show that this generalized mean-squared displacement in principle contains all information on the real mean-square displacement accessible in the instrumental time window. The derived formula provides a clear understanding of the effects of instrumental resolution on the apparent mean-squared displacement. Finally, we show that the generalized mean-square displacement can be used as a model-free indicator on confinement effects within the instrumental time window.

Electrostatics of the protein-water interface and the dynamical transition in proteins

Atomic displacements of hydrated proteins are dominated by phonon vibrations at low temperatures and by dissipative large-amplitude motions at high temperatures. A crossover between the two regimes is known as a dynamical transition. Recent experiments indicate a connection between the dynamical transition and the dielectric response of the hydrated protein. We analyze two mechanisms of the coupling between the protein atomic motions and the protein-water interface. The first mechanism considers viscoelastic changes in the global shape of the protein plasticized by its coupling to the hydration shell. The second mechanism involves modulations of the local motions of partial charges inside the protein by electrostatic fluctuations. The model is used to analyze mean-square displacements of iron of metmyoglobin reported by Mössbauer spectroscopy. We show that high displacement of heme iron at physiological temperatures is dominated by electrostatic fluctuations. Two onsets, one arising from the viscoelastic response and the second from electrostatic fluctuations, are seen in the temperature dependence of the mean-square displacements when the corresponding relaxation times enter the instrumental resolution window.

Looking for action

This paper considers the embodied nature of discourse for a professional work setting. It examines language in interaction in the airline cockpit, and specifically how shifts in pilots’ eye gaze direction can indicate the action of talk, that is, what talk is doing and its relative contribution to work-in-progress. Looking towards the other pilot’s face treats talk as occurring outside the predictable and scripted sequential flow of interaction for work. The talk might be casual conversation unrelated to work tasks, or involve negotiation of work arising from locally contingent circumstances. Pilots treat particular sites for looking, cockpit instrument panels and windows, as a home position for gaze for planned and predictable work activity. Looking away from this home position, as either speaker or recipient, treats talk as doing something else. The paper draws on insights and methods of conversation analysis, and uses naturally occurring data, video recordings of pilots at work on actual scheduled passenger flights.

Looking for action

This paper considers the embodied nature of discourse for a professional work setting. It examines language in interaction in the airline cockpit, and specifically how shifts in pilots’ eye gaze direction can indicate the action of talk, that is, what talk is doing and its relative contribution to work-in-progress. Looking towards the other pilot’s face treats talk as occurring outside the predictable and scripted sequential flow of interaction for work. The talk might be casual conversation unrelated to work tasks, or involve negotiation of work arising from locally contingent circumstances. Pilots treat particular sites for looking, cockpit instrument panels and windows, as a home position for gaze for planned and predictable work activity. Looking away from this home position, as either speaker or recipient, treats talk as doing something else. The paper draws on insights and methods of conversation analysis, and uses naturally occurring data, video recordings of pilots at work on actual scheduled passenger flights.

Evidence-Based Perspective on the Effect of Automobile-Related Modifications on the Driving Ability, Performance, and Safety of Older Adults

A systematic review of literature related to the impact of modifications made to automobiles on the driving ability, performance, and safety of older adults was completed as a part of the Evidence-Based Literature Review Project of the American Occupational Therapy Association. This review evaluated research on high-tech options, such as advanced technology systems (Intelligent Transportation Systems) currently in active development by manufacturers and researchers and the effect of features such as the instrument panel and window tinting. Although the evidence related to Intelligent Transportation Systems is inconclusive, studies have indicated that older adults would use selected technology options. Aftermarket window tinting negatively affects older adults' driving performance, and no evidence demonstrates that hydrophobic window treatment improves driving performance. The implications for occupational therapy practice, research, and education also are discussed.

A system to perform quantitative fluorescein angiography

Abstract Purpose: To develop a system with which fluorescein angiograms may be quantitatively compared across time, patients and laboratories. Methods: Sets of standard solutions of the fluorescein were developed in media that mimics the physical and chemical environments of compartments of the eye, i.e., serum and vitreous, in which the measurement is taken. Images from these sets of standards were obtained at exactly the same time and under the same instrument settings as the data from the eye on the same angiogram. Computer software was developed to quantitatively analyze the angiogram that established calibration plots and converted the grey image to an absolute color scale image of the data, as well as provide quality control information as to the performance of the instrument. Results: The position and shape of the excitation and emission spectra of the fluorescein standards matched those of fluorescein in serum and vitreous media. The 80% reduction in quantum efficiency of fluorescein in serum compared to fluorescein in PBS at pH 7.4 was equal to fluorescein in synthetic serum and/or PBS at pH 5.5. The reduction in quantum efficiency of fluorescein in vitreous was only 3% and equal to fluorescein in PBS at pH 7.3.The resulting computer generated color scale angiogram images were directly compared across time and patients and the initial results appeared consistent and reasonable. In addition, by evaluating the calculated instrument performance parameters, e.g., linearity, dynamic range, detection threshold and Window of Anaylsis, a determination of the quality of the angiogram could be made. Conclusions: This system provides data that is independent of the instrument and operator, and promises that quantitative comparisons can be made across time, patients and laboratories.

Promotion of Regenerative Processes in Injured Peripheral Nerve Induced by Low-Level Laser Therapy

This study aimed to assess in vitro the influence of low-level laser therapy (LLLT) on the regenerative processes of a peripheral nerve after trauma. In peripheral nerve injury initiated after severing due to accident or by a surgeon during operation, photomodulation by light in the red to near-infrared range (530-1000 nm) using low-energy lasers has been shown to accelerate nerve regeneration. Twenty-four New Zealand adult male rabbits were randomly assigned to two equal groups (control and laser-treated). General anesthesia was administered intramuscularly, and exploration of the peroneal nerve was done in the lateral aspect of the left leg. Complete section of the nerve was performed, which was followed by suturing of the neural sheath (epineurium). Irradiation was carried out directly after the operation and for 10 consecutive days. The laser used was diode with wavelength of 901 nm (impulsive) and power of 10 mW; it was a square-shaped window type (16 cm(2)), and its energy was applied by direct contact of the instrument's window to the site of the operation. Three rabbits from each group were sacrificed at the end of weeks 2, 4, 6, and 8, and specimens were collected from the site of nerve suturing and sent for histopathological examination. Two important factors were examined via histopathology: diameter of the nerve fibers and individual internodal length. Compared to the control group, significant variations in regeneration were observed, including thicker nerve fibers, more regular myelin layers, clearer nodes of Ranvier with absence of short nodes in the treated group. Variations between the two groups for diameter were significant for the 2(nd) week (p < 0.05), highly significant for the 4(th) and 6(th) weeks, respectively (p < 0.01), and very highly significant for the 8(th) week (p < 0.001). Variations between the two groups for internodal length were highly significant for the 2(nd) and 4(th) weeks (p < 0.01), and very highly significant for the 6(th) and 8(th) weeks (p < 0.001). This experiment affirms the beneficial effect of LLLT on nerve regeneration, since LLLT produced a significant amount of structural and cellular change. The results of the present study suggest that laser therapy may be a viable approach for nerve regeneration, which may be of clinical relevance in scheduled surgery or microsurgery.

Mid-infrared instruments on the Gemini 8-m telescopes

The mid-infrared instruments, operating in the 10 and 20 μm atmospheric windows, on the Gemini 8-m telescopes are described. The advantages and disadvantages of ground-based telescopes compared to satellite observatories are briefly discussed. On Gemini-N, Michelle, a cryogenic imager and grating and echelle spectrometer built at the UK Astronomy Technology Centre in Edinburgh offers imaging, long-slit spectroscopy and polarimetry. Spectral resolving powers between 200 and 20,000 are available by selecting one of five interchangeable gratings held in the cold grating drum. The Thermal Region Camera-Spectrometer (TReCS) is undergoing final tests at the University of Florida before delivery to Gemini-S. It offers imaging and low or moderate resolving power ( R<1000) spectroscopy. Even with the excellent image quality and low-emissivity of the Gemini telescopes, the thermal background from the sky, telescope and instrument windows are many orders of magnitude greater than the mid-infrared background emission in space. The main advantages of the Gemini instruments are the high spatial resolution available from large aperture ground-based telescopes (FWHM ∼ λ/ D=0.3 arcsec at 12 μm), the versatile instrumentation and the high spectral resolution, which coupled with the 50 m 2 collecting area, gives good spectroscopic performance. Some initial performance figures and results are given.

Fourier Transform Infrared and Quasi-Elastic Neutron Scattering Investigations on the Binding States and the Dynamics of Benzene Molecules in the Pores of MCM-41 Molecular Sieves

The in-plane C−H/C−C, out-of-plane C−H, and the fundamental ν19 C−C stretch vibrations of benzene molecules were monitored by FTIR spectroscopy, for adsorption in MCM-41 at room temperature and at different loadings. The results were compared with the corresponding data on ZSM-5 zeolites. The frequency and the relative intensity of IR bands point to the development of a compressed state of benzene in the pores of MCM-41, the density of which depended upon loading and lay in general between that of bulk liquid and a solidlike phase formed in the pores of ZSM-5 zeolite on benzene adsorption. Quasi-elastic neutron scattering results reveal that the pore characteristics play a crucial role in deciding the dynamics of benzene molecules in a confined medium. Thus, in contrast to the molecular motions of benzene in ZSM-5 zeolite where only rotational motion was observed in the instrumental time window of 10-10−10-12 s, the benzene molecules adsorbed in MCM-41 exhibit only translational motion. Further, the value...

The extended surface forces apparatus. II. Precision temperature control

We describe the design and performance of a low-cost, bidirectional temperature control system with very high stability and low thermal gradients in a working range from −10 to 70 °C. System elements such as thermal insulation, thermal pumps, and feedback control as well as safety features are discussed. The performance of the entire system under realistic experimental conditions is documented. Precise temperature control has led to significantly improved instrumental stability. An extension of the instrumental window towards slower measurements has been made possible. This temperature-control system is presented in the framework of the extended surface forces apparatus but is also applicable to other scientific instruments that require subnanometer positioning stability over extended periods of time.

A high resolution quasielastic neutron scattering study of the guest molecules dynamics in the cyclohexane/thiourea inclusion compound

In cyclohexane/thiourea inclusion compounds, the host substructure contains uni-directional and non-intersecting channels within which the guest (cyclohexane) molecules are located. There are three thermotropic structural phases in cyclohexane/thiourea: phase I (down to 149 K) is rhombohedral, phase II (149–129 K) is monoclinic and phase III (below 129 K) is also monoclinic . In this paper, we report high resolution (1 μeV) incoherent quasielastic neutron scattering experiments performed in the three phases of the inclusion compound. We show that a quasielastic broadening is observed only in phase III, whereas the dynamics of the guest molecules in phases II and I is too fast to be analysed within the instrumental energy window. In phase III, the cyclohexane molecule undergoes 120° jumps about its three-fold symmetry axis with an activation energy E a=9.6(±0.5) kJ mol −1, the three-fold symmetry axis of cyclohexane being tilted by an angle λ=75° with respect to the channel axis. These experiments confirm the orientational ordering of the guest molecules in phase III of the inclusion compound.

Microcanonical analysis of the kinetic method.: The meaning of the “effective temperature”

An analytical expression for the “effective temperature” parameter in the Cooks kinetic method is derived using classical Rice–Ramsperger–Kassel (RRK) theory for the microcanonical unimolecular dissociation rate. The approximate expression is appropriate for metastable ion dissociation experiments and high ion source temperatures. The effective temperature is directly proportional to the well depth (complexation energy) of the dissociating cluster ion, is inversely proportional to the number of oscillators of the cluster (vibrational degrees of freedom), and also depends on the product of the reaction frequency (preexponential factor) and the instrumental time window of the experiment. Numerical simulations using classical RRK rates with a detailed kinetics treatment are compared with the analytical expression for the effective temperatures. For fast dissociations (shallow cluster well depth or small number of oscillators), threshold effects cause significant curvature in the kinetic method plots. The implications of these results on the accuracy of relative thermochemical measurements by the kinetic method are discussed.

The Monolithic Double-Crystal Spectrometer: Theory and Design Principles

The monolithic double-crystal spectrometer (MDCS) is a perfect-crystal device allowing X-ray spectroscopic measurements on an absolute energy scale with an accuracy of better than 1 in 106. This paper presents a detailed analysis of its properties using the dynamical theory of X-ray propagation in perfect crystals. The transmitted wavelength, the transmission window profile, the energy dispersion and the integrated intensity of the transmitted radiation and their dependence on the scanning angle of rotation are derived. The polarization mixing is shown to have a subtle yet important effect on the transmission of the MDCS. An example of a specific MDCS, designed for measuring the Cu Kβ emission spectra, is discussed in detail. The results of the study highlight the advantages and limitations of this device and yield tools for optimizing the MDCS for a wide class of X-ray spectroscopic measurements and for correcting the inevitable, although minimal, distortions introduced by the finite instrumental window of the device.

Nonlocal Reactive Transport with Physical and Chemical Heterogeneity: Localization Errors

The origin of nonlocality in “macroscale” models for subsurface chemical transport is illustrated. It is argued that media that are either nonperiodic (e.g., media with evolving heterogeneity) or periodic viewed on a scale wherein a unit cell is discernible must display some nonlocality in the mean. A metaphysical argument suggests that owing to the scarcity of information on natural scales of heterogeneity and on scales of observation associated with an instrument window, constitutive theories for the mean concentration should at the outset of any modeling effort always be considered nonlocal. The intuitive appeal to nonlocality is reinforced with an analytical derivation of the constitutive theory for a conservative tracer without appeal to any mathematical approximations. Deng et al. (1993) present a first‐order, nonlocal, Eulerian theory for transport of a conservative solute in an infinite nondeforming domain under steady flow conditions. Hu et al. (this issue) extended these results to account for nonequilibrium linear sorption with random partition coefficient Kd but deterministic constant reaction rate Kr. These theories are localized herein, and comparisons are made between the fully nonlocal (FNL), nonlocal in time (NLT), and fully localized (FL) theories. For conservative transport, there is little difference between the first‐order FL and FNL models for spatial moments up to and including the third. However, for conservative transport the first‐order NLT model differs significantly from the FNL model in the third spatial moments. For reactive transport, all spatial moments differ between the FNL and FL models. The second transverse‐horizontal and third longitudinal‐horizontal moments for the NLT model differ from the FNL model. These results suggest that localized first‐order transport models for conservative tracers are reasonable if only lower‐order moments are desired. However, when the chemical reacts with its environment, the localization approximation can lead to significant error in all moments, and a FNL model will in general be required for accurate simulation.

Bromide Transport Detection in Tilled and Nontilled Soil: Solution Samplers vs. Soil Cores

AbstractExperimental validation of solute transport models is often met with unsatisfying or ambiguous results. Aside from the inherent difficulty in conducting these experiments, the lack of a standard set of methodologies employed in these studies may be an impediment. This study was conducted to determine if the method employed in the sampling of soil solutes could influence the results of model validation attempts. A narrow pulse of KBr was uniformly applied to two 25‐m2 plots, one tilled and the other undisturbed, on a level Ulm clay loam (fine, montmorillonitic, mesic Ustollic Haplargid). Solute movement was then monitored for the next 388 d using replicated ceramic cup solution samplers at depths of 0.15, 0.30, 0.80, 1.20, 1.60, and 2.00 m and by the periodic removal of replicate soil cores in 0.05‐m increments to a maximum depth of 3.70 m. Overall, the methods yielded consistent information regarding the mean convective transport of Br−. Both methodologies indicated deeper and more rapid movement of Br− in the nontilled soil, although the shallow solution samplers appear to miss the most rapidly moving solute. By the conclusion of the experiment, the difference between the centers of mass of the Br− plumes in the tilled and nontilled soil was at least 0.6 m. The soil core and solution sampler methods appear to yield inconsistent measures of the solute dispersion but we attribute the differences to the effects of incomplete mass recovery and, we argue, follow naturally from the instrument window of the sampling methodology relative to the observed soil heterogeneity.