Nondestructive ultrasonic measurement of bolt preload using the pulsed-phase locked-loop interferometer

Achieving accurate preload in threaded fasteners is an important and often critical problem which is encountered in nearly all sectors of government and industry. Conventional tensioning methods which rely on torque carry with them the disadvantage of requiring constant friction in the fastener in order to accurately correlate torque to preload. Since most of the applied torque typically overcomes friction rather than tensioning the fastener, small variations in friction can cause large variations in preload. An instrument called a pulsed phase locked loop interferometer, which was recently developed at NASA Langley, has found widespread use for measurement of stress as well as material properties. When used to measure bolt preload, this system detects changes in the fastener length and sound velocity which are independent of friction. The system is therefore capable of accurately establishing the correct change in bolt tension. This high resolution instrument has been used for precision measurement of preload in critical fasteners for numerous applications such as the space shuttle landing gear and helicopter main rotors

Risk Factors Associated With Osteoarthritis Post-ACL Injury: A Literature Review

Background: Anterior cruciate ligament ruptures are a relatively common injury in both contact and non-contact sports and are known to have a long rehabilitation process. In addition to a long recovery to get back to competitive sport levels, ACL tears are also associated with a high risk of early onset osteoarthritis, resulting in pain, functional limitations, and a diminished quality of life. There are many variables that have been studied that have a correlation to the occurrence of this condition. Objectives: To examine peer reviewed literature to determine evidence based risk factors for developing osteoarthritis post-ACL injury. Data sources: Resources were pulled from PubMed, SPORTDiscus, and MEDLINE, between the years of 1999 and 2016 using the key words anterior cruciate ligament, ACL, osteoarthritis, and risk factors. Inclusion criteria consisted of the following: peer reviewed studies that were published after 1999, studies that were done on human subjects, ACL ruptures that were treated by either conservative management, patella graft, or hamstring graft, and radiographic follow-up five years or more post-surgery. Abstracts and unpublished data were excluded. Conclusion: There are seven important factors associated with the incidence of post-traumatic osteoarthritis following ACL injury. Treatment decisions, graft choice, meniscal status, age at the time of reconstruction, time between injury and reconstruction, sport activity post-injury, and body mass index all play a role in the development of OA. Some variables can be controlled, while others cannot, which makes it difficult to entirely diminish the occurrence of OA

An XMM-Newton View of the Radio Galaxy 3C 411

We present the first high signal-to-noise XMM-Newton observations of the broad-line radio galaxy 3C 411. After fitting various spectral models, an absorbed double power-law continuum and a blurred relativistic disk reflection model (kdblur) are found to be equally plausible descriptions of the data. While the softer power-law component ($\Gamma$=2.11) of the double power-law model is entirely consistent with that found in Seyfert galaxies (and hence likely originates from a disk corona), the additional power law component is very hard ($\Gamma$=1.05); amongst the AGN zoo, only flat-spectrum radio quasars have such hard spectra. Together with the very flat radio-spectrum displayed by this source, we suggest that it should instead be classified as a FSRQ. This leads to potential discrepancies regarding the jet inclination angle, with the radio morphology suggesting a large jet inclination but the FSRQ classification suggesting small inclinations. The kdblur model predicts an inner disk radius of at most 20 r$_g$ and relativistic reflection

The effect of tetrathionate on the stability and immunological properties of muscle triosephosphate dehydrogenases

Tetrathionate effect on stability and immunological properties of muscle triosephosphate dehydrogenase

The issuance of series-1996 $100 Federal Reserve notes: goals, strategy, and likely results.

In March 1996, the Federal Reserve began issuing series-1996 $100 Federal Reserve notes. Culminating a cooperative effort by the U.S. Department of the Treasury and the Federal Reserve System that dated from the 1980s, the series-1996 note was the first major design change in U.S. currency in sixty-six years. The new note was developed to provide better protection for users of U.S. currency against the growing threat of counterfeiting, especially that posed by increasingly affordable and capable color scanning and printing systems. This article discusses the Federal Reserve's strategy for issuing newly designed$100 notes and says that it appears likely to achieve its objectives: a replacement of pre-series-1996 $100 notes that is timely in relation to the developing threat of counterfeiting, with a minimum impact on holders and users of those notes throughout the world.Money

Influence of Visual Feedback On Dynamic Balance Control in Chronic Stroke Survivors

Chronic stroke survivors have an increased incidence of falls during walking, suggesting changes in dynamic balance control post-stroke. Despite this increased incidence of falls during walking, balance control is often studied only in standing. The purpose of this study was to quantify deficits in dynamic balance control during walking, and to evaluate the influence of visual feedback on this control in stroke survivors. Ten individuals with chronic stroke, and ten neurologically intact individuals participated in this study. Walking performance was assessed while participants walked on an instrumented split-belt treadmill with different types of visual feedback. Dynamic balance control was quantified using both the extent of center of mass (COM) movement in the frontal plane over a gait cycle (COM sway), and base of support (step width). Stroke survivors walked with larger COM sway and wider step widths compared to controls. Despite these baseline differences, both groups walked with a similar ratio of step width to COM sway (SW/COM). Providing a stationary target with a laser reference of body movement reduced COM sway only in the stroke group, indicating that visual feedback of sway alters dynamic balance control post-stroke. These results demonstrate that stroke survivors attempt to maintain a similar ratio of step width to COM movement, and visual cues can be used to help control COM movement during walking post-stroke

The investigation of critical pressure burning of fuel droplets Annual report, 1 Jan. - 31 Dec. 1970

Experimental and theoretical results of critical pressure burning of fuel droplet

Functional Implications of Impaired Control of Submaximal Hip Flexion Following Stroke

Introduction: We quantified sub-maximal torque regulation during low to moderate intensity isometric hip flexion contractions in individuals with stroke and the associations with leg function. Methods: 10 participants with chronic stroke and 10 controls performed isometric hip flexion contractions at 5%, 10%, 15%, 20%, and 40% of maximal voluntary contraction (MVC) in paretic, non-paretic, and control legs. Results: Participants with stroke had larger torque fluctuations (coefficient of variation, CV), for both the paretic and non-paretic legs, than controls (Pr2 =0.45) and Berg Balance Score (r2=0.38). At 5% MVC, there were larger torque fluctuations in the contralateral leg during paretic contractions compared with the control leg. Conclusions: Impaired low-force regulation of paretic leg hip flexion can be functionally relevant and related to control versus strength deficits post stroke