Jon R. Pratt
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View article: Ultralow loss torsion micropendula for chipscale gravimetry
Ultralow loss torsion micropendula for chipscale gravimetry Open
We explore a new class of chipscale torsion pendula formed by Si$_3$N$_4$ nanoribbon suspensions. Owing to their unique hierarchy of gravitational, tensile, and elastic stiffness, the devices exhibit damping rates of $\sim 10\;μ$Hz and par…
View article: Microscale torsion resonators for short-range gravity experiments
Microscale torsion resonators for short-range gravity experiments Open
Measuring gravitational interactions on sub-100-$μ$m length scales offers a window into physics beyond the Standard Model. However, short-range gravity experiments are limited by the ability to position sufficiently massive objects to with…
View article: Nanoscale Torsional Dissipation Dilution for Quantum Experiments and Precision Measurement
Nanoscale Torsional Dissipation Dilution for Quantum Experiments and Precision Measurement Open
The quest for ultrahigh-Q nanomechanical resonators has driven intense study of strain-induced dissipation dilution, an effect whereby vibrations of a tensioned plate are effectively trapped in a lossless potential. Here, we show for the f…
View article: Nanoscale torsional dissipation dilution for quantum experiments and precision measurement
Nanoscale torsional dissipation dilution for quantum experiments and precision measurement Open
We show that torsion resonators can experience massive dissipation dilution due to nanoscale strain, and draw a connection to a century-old theory from the torsion balance community which suggests that a simple torsion ribbon is naturally …
View article: Verification of an in situ calibrated optomechanical accelerometer for use as a strong ground motion seismic reference
Verification of an in situ calibrated optomechanical accelerometer for use as a strong ground motion seismic reference Open
Optomechanical accelerometers offer in situ traceability to the international system of units through laser interferometry, providing an alternative to a calibration chain using instrumented shakers. Here, we examine the ‘self-calibrating’…
View article: Issue Information
Issue Information Open
Two novel unstable hemoglobin variants due to in-frame deletions of key amino acids in the β-globin chain Zebrafish larvae as a model to demonstrate secondary iron overloadThe 2014 BCSH criteria and the 2016 WHO criteria for essential thro…
View article: Evaluation of the accuracy, consistency, and stability of measurements of the Planck constant used in the redefinition of the international system of units
Evaluation of the accuracy, consistency, and stability of measurements of the Planck constant used in the redefinition of the international system of units Open
The Consultative Committee for Mass and related quantities (ccm), of the International Committee for weights and measures (cipm), has recently declared the readiness of the community to support the redefinition of the international system …
View article: Measurement of the Planck constant at the National Institute of Standards and Technology from 2015 to 2017
Measurement of the Planck constant at the National Institute of Standards and Technology from 2015 to 2017 Open
Researchers at the National Institute of Standards and Technology(NIST) have measured the value of the Planck constant to be $h =6.626\,069\,934(89)\times 10^{-34}\,$J$\,$s (relative standard uncertainty $13\times 10^{-9}$). The result is …
View article: Bridging classical and quantum mechanics
Bridging classical and quantum mechanics Open
Using a watt balance and a frequency comb, a mass-energy equivalence is derived. The watt balance compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and …
View article: Monitoring gravity for the NIST-4 watt balance
Monitoring gravity for the NIST-4 watt balance Open
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View article: Invited Article: A precise instrument to determine the Planck constant, and the future kilogram
Invited Article: A precise instrument to determine the Planck constant, and the future kilogram Open
A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and …
View article: Coil motion effects in watt balances: a theoretical check
Coil motion effects in watt balances: a theoretical check Open
A watt balance is a precision apparatus for the measurement of the Planck constant that has been proposed as a primary method for realizing the unit of mass in a revised International System of Units. In contrast to an ampere balance, whic…
View article: A LEGO Watt balance: An apparatus to determine a mass based on the new SI
A LEGO Watt balance: An apparatus to determine a mass based on the new SI Open
A global effort to redefine our International System of Units (SI) is underway, and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed…
View article: A Determination of the Local Acceleration of Gravity for the NIST-4 Watt Balance
A Determination of the Local Acceleration of Gravity for the NIST-4 Watt Balance Open
A new watt balance is being constructed at the National Institute of\nStandards and Technology (NIST) in preparation for the redefinition of the\nInternational System of Units and the realization of mass through an exact\nvalue of the Plan…