Measurement of the intrinsic sensitivity for a single-ended accelerometer without the influence of the mounting condition

Microphones are designed to respond to acoustic pressure fields, but they can also be excited by external sources of mechanical vibration. In hearing aids, feedback is a difficult problem to resolve due to the high gain used to amplify sounds. The problem is worsened by the location of microphones and loudspeakers in close proximity, coupling both the acoustic and mechanical feedback paths. The first proposals of microphone vibration measurement techniques and definitional structure were published by Mead Killion in the 1970’s. Significant improvements in measurement technique have been published over the last 10 years. This talk will focus on a new measurement technique that allows for direct measurement of the “intrinsic vibration sensitivity.” The technique gives the ideal zero acoustic pressure condition at the microphone port and isolates room acoustic noise from the desired vibration signal. The noise floor of the new technique is 30dB below Z axis measurement, allowing for exceptionally clean measurement of primary-axis vibration sensitivity up to 10 kHz. Improvements are robust enough to enable the clean measurement of off-axis sensitivity of the microphone, which is often below 50 dB SPL equivalent at 9.81 m/s^2 of acceleration.

Microphones are designed to respond to acoustic pressure fields, but they can also be excited by external sources of mechanical vibration. In hearing aids, feedback is a difficult problem to resolve due to the high gain used to amplify sounds. The problem is worsened by the location of microphones and loudspeakers in close proximity, coupling both the acoustic and mechanical feedback paths. The first proposals of microphone vibration measurement techniques and definitional structure were published by Mead Killion in the 1970’s. Significant improvements in measurement technique have been published over the last 10 years. This talk will focus on a new measurement technique that allows for direct measurement of the “intrinsic vibration sensitivity”. The technique gives the ideal zero acoustic pressure condition at the microphone port and isolates room acoustic noise from the desired vibration signal. The noise floor of the new technique is 30 dB below previous methods, allowing for exceptionally clean measurement of primary-axis vibration sensitivity up to 10 kHz. Improvements are robust enough to enable the clean measurement of off-axis sensitivity of the microphone, which is often below 50 dBspl equivalent at 9.81 m/s2 of acceleration.

LWA1 is a new radio telescope operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 258 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable features of the instrument include high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and 4 independently-steerable beams utilizing digital "true time delay" beamforming. This paper summarizes the design of LWA1 and its performance as determined in commissioning experiments. We describe the method currently in use for array calibration, and report on measurements of sensitivity and beamwidth.

In vitro intrinsic radiation sensitivity of glioblastoma multiforme

Heteromultimerization between different potassium channel subunits can generate channels with novel functional properties and thus contributes to the rich functional diversity of this gene family. The inwardly rectifying potassium channel subunit Kir5.1 exhibits highly selective heteromultimerization with Kir4.1 to generate heteromeric Kir4.1/Kir5.1 channels with unique rectification and kinetic properties. These novel channels are also inhibited by intracellular pH within the physiological range and are thought to play a key role in linking K+ and H+ homeostasis by the kidney. However, the mechanisms that control heteromeric K+ channel assembly and the structural elements that generate their unique functional properties are poorly understood. In this study we identify residues at an intersubunit interface between the cytoplasmic domains of Kir5.1 and Kir4.1 that influence the novel rectification and gating properties of heteromeric Kir4.1/Kir5.1 channels and that also contribute to their pH sensitivity. Furthermore, this interaction presents a structural mechanism for the functional coupling of these properties and explains how specific heteromeric interactions can contribute to the novel functional properties observed in heteromeric Kir channels. The highly conserved nature of this structural association between Kir subunits also has implications for understanding the general mechanisms of Kir channel gating and their regulation by intracellular pH.

We have proposed and demonstrated a novel elastic optical fiber Fabry–Perot interferometer (FPI)-based ac magnetic field sensor with high magnetic sensitivity and correction of temperature crosstalk. The elastic FPI is formed by soft splicing using low Young’s modulus polydimethylsiloxane material at the joint point of a hollow-core fiber and single-mode fibers and is fixed on a common supermendur rod, a kind of magnetostrictive material. AC magnetic field-induced length change of the magnetostrictive rod results in the obvious change of the FPI cavity length and finally is transduced to the intensity variation of the sensor signal, which makes the sensor highly sensitive to ac magnetic field. Taking advantage of the elastic FPI structure, the magnetic sensitivity (in terms of strain) is improved to 48 ppm/mT (75.01 pm/mT in terms of wavelength), compared with the low intrinsic sensitivity of the conventional magnetostrictive rod (usually below several ppm/mT and 0.39 ppm/mT in our case). Moreover, the impact of temperature cross-sensitivity is removed by retrieving the wavelength shift of the FPI interference spectrum based on the calibrated signal voltage versus wavelength shift. All the ac magnetic fields of different frequencies and intensities have been successfully detected and measured by our FPI sensor without the impact of temperature crosstalk. We believe such a simple, compact, and cost-effective sensor would be a promising candidate for accurate monitoring of ac magnetic field.

Limits due to instrumental polarisation in CMB experiments at microwave wavelengths

A robust performance evaluation method for vapor cells used in magnetometers is proposed in this work. The performance of the vapor cell determines the sensitivity of the magnetic measurement, which is the core parameter of a magnetometer. After establishing the relationship between intrinsic sensitivity and the total relaxation rate, the total relaxation rate of the vapor cell can be obtained to represent the intrinsic sensitivity of the magnetometer by fitting the parameters of the magnetic resonance experiments. The method for measurement of the total relaxation rate based on the magnetic resonance experiment proposed in this work is robust and insensitive to ambient noise. Experiments show that, compared with conventional sensitivity measurement, the total relaxation rate affected by magnetic noise below 0.9 nT, pump light frequency noise below 1.5 GHz, pump light power noise below 9%, probe light power noise below 3% and temperature fluctuation of 150 ± 3 °C deviates by less than 2% from the noise-free situation. This robust performance evaluation method for vapor cells is conducive to the construction of a multi-channel high-spatial-resolution cardio-encephalography system.

Magnetic Resonance Imaging (MRI) techniques provide a non‐invasive method for the highly accurate anatomic depiction of the heart and vessels. Most MR‐sequences demonstrate more or less significant sensitivity to flow and motion, which can lead to artifacts in many applications. The intrinsic motion sensitivity of MRI can, however, also be used to image vessels like in phase contrast (PC) MR‐angiography or to quantify blood flow and motion of tissue. Such techniques offer the unique possibility to acquire spatially registered functional information simultaneously with the morphological data within a single experiment. Characterizations of the dynamic components of blood flow and cardiovascular function provide insight into normal and pathological physiology and have made considerable progress in recent yearsTo synchronize flow or motion sensitive measurements with periodic tissue motion or pulsatile flow, data acquisition is typically gated to the cardiac cycle and time resolved (CINE) anatomical images are collected to depict the dynamics of tissue motion and blood flow during the cardiac cycle. Visualization and quantification of blood flow and tissue motion using PC MRI has been widely used in a number of applications. In addition to analyzing tissue motion such as left ventricular function, time‐resolved 2D PC MRI techniques have proven to be useful tools for the assessment of blood flow within the cardiovascular system.Moreover, 3D spatial encoding offers the possibility of isotropic high spatial resolution and thus the ability to measure and visualize the temporal evolution of complex flow and motion patterns in a 3D‐volume. In this context, ECG synchronized and respiration controlled flow sensitive 3D MRI using 3‐directional velocity encoding (also termed ‘flow sensitive 4D MRI’) can be employed to detect and visualize global and local blood flow characteristics in targeted vascular regions (aorta, cranial arteries, carotid arteries, etc.). For the analysis and visualization of complex, three‐directional blood flow within a 3D volume, various visualization tools, including 2D vector‐fields, 3D streamlines and particle traces, have been reported. In addition more advanced data quantification strategies of directly measured (e.g. flow rates) or derived parameters (e.g. pressure difference maps, wall sheer stress, pulse wave velocity, etc.) are promising as new clinical markers for the characterization of cardiovascular disease.This lecture will provide an overview of the MR imaging principles and advanced acquisition methods, data processing, flow visualization and quantification strategies, and clinical applications of flow sensitive MRI imaging.Learning Objectives:1. Understand the basic and advanced methods for flow measurements using MRI2. Understand techniques for 3D flow visualization and quantification of blood flow and derived parameters3. Understand the issues related to clinical applications of flow‐sensitive MRI

Proteins are widely used biomarkers in disease diagnosis. A vast majority of clinical methods for the detection of the marker proteins use antibodies. Such methods are sub-optimal to function in global health applications and point-of-care assays. We are developing single-walled carbon nanotube-based optical sensors for straight-forward, rapid and sensitive measurement of proteins for accurate disease diagnosis. Single-walled carbon nanotubes, with intrinsic photoluminescence and high optical sensitivity towards molecular interactions, upon the surface modification with polymeric materials provide unmatched basis for the development of optical sensors.

Phase-interrogated surface plasmon resonance sensor based on laser feedback interferometry

The strain sensitivity measurements of Dupont 1400Biroxr thick-film resistor materials in untrimmed and laser trimmed conditions are described. This was studied to better understand the post-laser trim drift phenomenon and evaluate the effect of packaging/assembly induced stresses on the resistors. The strain coefficient of resistance or the strain sensitivity of the untrimmed 102_ 106 \Omega / \Box$^b$ resistor materials is small, reversible, and independent of resistor geometry or fired thickness (t f ). This strain sensitivity (?i) is an intrinsic material property which is determined by the conduction mechanism in the material. The strain sensitivity of the laser trimmed · resistors is a sum of the intrinsic sensitivity (?i) and an additional term called the extrinsic strain sensitivity (\gamma ex ). The additional extrinsic contribution can be large and irreversible and depends strongly on the fired thickness (t f of the resistor. A mechanism is proposed to explain these observations. The mismatch of the thermal expansion coefficients of the resistor material and the substrate leads to high internal stresses in the thick resistor. Hence crack formation and propagation is easier which leads to increased strain sensitivity (extrinsic) and post-trim drift. It was experimentally determined that Al 2 O 3 from the substrate dissolved 6-8 µm into the thick-film resistor during resistor firing. For thin resistors the relatively higher amount of dissolved Al 2 O 3 from the substrate in the resistor glass reduces the thermal expansion mismatch between the fired resistor and substrate. Thus its strain sensitivity and drift are much smaller than a thicker fired resistor.