Design of a precision tilt and vibration isolation system

Precision tilt and vibration isolation system desig

Limitations on inertial sensor testing produced by test platform vibrations

Limitations on inertial sensor testing produced by test platform vibration

Inelastic diffractive scattering in nonperturbative QCD

We examine diffractive proton-proton scattering p p -> p X and photo- and electroproduction of \rho^0 mesons \gamma^(*) p -> \rho^0 X, where X denotes a proton or a final state, into which the proton can go by diffractive dissociation. Using a functional integral approach we derive the scattering amplitudes, which are governed by the expectation values of light-like Wegner-Wilson loops, which are then evaluated using the model of the stochastic vacuum. For the proton, we assume a quark-diquark structure. From the scattering amplitudes we calculate total and differential cross sections for high centre of mass energy and small momentum transfer and compare with experiments. Furthermore we calculate isovector form factors for the proton and the pion within the same model.Comment: 32 pages, 11 figures, v3: revised chapter 5, added appendix B, to be published in Eur.Phys.J.

Magnetometer suitable for Earth field measurement based on transient atomic response

We describe the development of a simple atomic magnetometer using $^{87}$Rb vapor suitable for Earth magnetic field monitoring. The magnetometer is based on time-domain determination of the transient precession frequency of the atomic alignment around the measured field. A sensitivity of 1.5 nT/$\sqrt{Hz}$ is demonstrated on the measurement of the Earth magnetic field in the laboratory. We discuss the different parameters determining the magnetometer precision and accuracy and predict a sensitivity of 30 pT/$\sqrt{Hz}$Comment: 6 pages, 5 figure

Imaging subsurface defects using SQUID magnetometers

Over the last several years, SQUID magnetometers have been utilized for detection of defects in metal structures by measuring the magnetic field produced by injected current or permanent magnetization [1,2,3]. Because the amplitude of the output signal from the SQUID magnetometer is independent of the frequency of the magnetic field to be measured, SQUIDs are suitable for dc or low frequency measurements as required for detection of subsurface flaws inside a conductor

Continuous ligand-assisted elution chromatography applied to separation of rare earth elements

Rare earth elements (REEs) are metals used to make many valuable products such as magnets and electronics. Following their extraction from larger materials, REEs are to be separated into their individual components as high purity is required for product manufacture. Purification is very difficult because most (15/17) of the REEs are lanthanides (Ln’s) and Ln ions have the same valence and similar atomic radii. The current industrial process for purifying REEs involves using toxic solvents to perform a series of liquid-liquid extractions. Ling and Wang (2015) proposed a ligand-assisted batch chromatography process to purify Ln’s. The latter approach is a vast improvement over the former in terms of safety, however being a batch process, it is not economical for industrial use. The purpose of this study was to design and test a continuous system based off of Ling and Wang’s ligand-assisted elution chromatography process. A titania sorbent was used with a selective ligand, ethylenediaminetetraacetic acid (EDTA). The continuous system utilizes a stepwise elution process and separates a solution of praseodymium (Pr) and samarium (Sm). A Semba Octave SMB chromatography system was used to perform the experiment. Yields and purities greater than 95% were seen for each of the components in solution and the process can be run indefinitely. This continuous process for Ln separation is of interest because safety is increased in comparison to the aforementioned industrial system, sorbent productivity is increased, and it is more robust and simpler to run than the batch process. This continuous system can be scaled up to produce high purity REEs safely and efficiently

There is a low rate of major adverse cardiovascular events in chest pain patients with a moderate risk heart score referred from urgent care for expedited outpatient cardiology evaluation: a multi-center study

Background The HEART score is an effective method of risk stratifying emergency department (ED) patients with chest pain. The rate of major adverse cardiovascular events (MACE) in patients with moderate HEART score referred from an urgent care (UC) for an expedited outpatient cardiology evaluation for 11 months was described in 133 patients in a previous study. This is a follow-up study with 18 months of data and 206 patients.Aim. The primary outcome was to examine the rate of MACE when patients with moderate HEART score were referred for an expedited outpatient cardiology follow-up after evaluation in urgent care. The secondary outcome was to determine if there is a decrease in rate of ED transfer after this protocol was introduced.Methods. A cross-sectional study was conducted by a multispecialty group in Las Vegas, Nevada, which included 206 patients with a HEART score of 4 to 6 (i.e.: moderate risk) who presented to one of five UC centers with chest pain or an anginal equivalent. A streamlined evaluation protocol to assess each HEART score component was adopted by all UC providers to facilitate an expedited outpatient cardiology follow-up, as an alternative to referral to the emergency department. Data was collected from February 14, 2019 through August 13, 2020. The population was followed for 6 weeks with a primary endpoint of MACE determined by electronic medical record review and direct phone contact with patients. Outcomes were confirmed in 98% of patients. Chest pain transfer data was compared between 12 months prior to implementing HEART protocol and 18 months of data analysis while using the new protocol.Results. Over the course of 18 months, 206 patients with a moderate risk HEART score were referred to outpatient cardiology in an expedited manner. The average age was 65 with 53% female and 47% male patients. 150 patients (73% of the 206) were seen within 3 days, 114 (55%) underwent stress testing, 6 (3%) had coronary computed tomography angiogram, and 6 (3%) received an invasive coronary angiogram. Five patients were found to have MACE: one patient who had a non-ST-elevation myocardial infarction and subsequent coronary stent, two patients were found to have obstructive disease after coronary angiography with subsequent coronary artery bypass graft, one patient had an abnormal stress test and subsequent coronary stent, and one patient had critical mitral stenosis, multi-vessel coronary artery disease and underwent coronary artery bypass graft with mitral valve replacement with complications of renal failure and COVID-19 and expired. The emergency department referral rate declined by 21%.Conclusion. Patients with a moderate risk HEART score referred from UC for an expedited outpatient cardiology evaluation had a low rate of MACE and no deaths due to delay of care. There was also a significant decrease in the rate of ED referrals.Background. The HEART score is an effective method of risk stratifying emergency department (ED) patients with chest pain. The rate of major adverse cardiovascular events (MACE) in patients with moderate HEART score referred from an urgent care (UC) for an expedited outpatient cardiology evaluation for 11 months was described in 133 patients in a previous study. This is a follow-up study with 18 months of data and 206 patients.Aim. The primary outcome was to examine the rate of MACE when patients with moderate HEART score were referred for an expedited outpatient cardiology follow-up after evaluation in urgent care. The secondary outcome was to determine if there is a decrease in rate of ED transfer after this protocol was introduced.Methods. A cross-sectional study was conducted by a multispecialty group in Las Vegas, Nevada, which included 206 patients with a HEART score of 4 to 6 (i.e.: moderate risk) who presented to one of five UC centers with chest pain or an anginal equivalent. A streamlined evaluation protocol to assess each HEART score component was adopted by all UC providers to facilitate an expedited outpatient cardiology follow-up, as an alternative to referral to the emergency department. Data was collected from February 14, 2019 through August 13, 2020. The population was followed for 6 weeks with a primary endpoint of MACE determined by electronic medical record review and direct phone contact with patients. Outcomes were confirmed in 98% of patients. Chest pain transfer data was compared between 12 months prior to implementing HEART protocol and 18 months of data analysis while using the new protocol.Results. Over the course of 18 months, 206 patients with a moderate risk HEART score were referred to outpatient cardiology in an expedited manner. The average age was 65 with 53% female and 47% male patients. 150 patients (73% of the 206) were seen within 3 days, 114 (55%) underwent stress testing, 6 (3%) had coronary computed tomography angiogram, and 6 (3%) received an invasive coronary angiogram. Five patients were found to have MACE: one patient who had a non-ST-elevation myocardial infarction and subsequent coronary stent, two patients were found to have obstructive disease after coronary angiography with subsequent coronary artery bypass graft, one patient had an abnormal stress test and subsequent coronary stent, and one patient had critical mitral stenosis, multi-vessel coronary artery disease and underwent coronary artery bypass graft with mitral valve replacement with complications of renal failure and COVID-19 and expired. The emergency department referral rate declined by 21%.Conclusion. Patients with a moderate risk HEART score referred from UC for an expedited outpatient cardiology evaluation had a low rate of MACE and no deaths due to delay of care. There was also a significant decrease in the rate of ED referrals

High-temperature superconducting fault current microlimiters

High-temperature superconducting microbridges implemented with YBa(2)Cu(3)O(7-delta) thin-films are shown to be possible fault current limiters for microelectronic devices with some elements working at temperatures below the superconducting critical temperature and, simultaneously, under very low power conditions (below 1W). This is the case in the important applications of superconductors as SQUID based electronics, and technologies for communication or infrared detectors. In this paper it is shown that the good thermal behavior of these microlimiters allows working in a regime where even relatively small faults induce their transition to highly dissipative states, dramatically increasing their limitation efficiency. The conditions for optimal refrigeration and operation of these microlimiters are also proposed.Comment: 10 pages, 3 figures. LaTeX and EPS file

Development and analysis of the Software Implemented Fault-Tolerance (SIFT) computer

SIFT (Software Implemented Fault Tolerance) is an experimental, fault-tolerant computer system designed to meet the extreme reliability requirements for safety-critical functions in advanced aircraft. Errors are masked by performing a majority voting operation over the results of identical computations, and faulty processors are removed from service by reassigning computations to the nonfaulty processors. This scheme has been implemented in a special architecture using a set of standard Bendix BDX930 processors, augmented by a special asynchronous-broadcast communication interface that provides direct, processor to processor communication among all processors. Fault isolation is accomplished in hardware; all other fault-tolerance functions, together with scheduling and synchronization are implemented exclusively by executive system software. The system reliability is predicted by a Markov model. Mathematical consistency of the system software with respect to the reliability model has been partially verified, using recently developed tools for machine-aided proof of program correctness