Noise of the Harrier in vertical landing and takeoff

The noise of the Harrier AV8C aircraft in vertical takeoff and landing was measured 100 feet to the side of the aircraft where jet noise dominates. The noise levels were quite high - up to 125 dB overall sound level at 100 feet. The increased noise due to jet impingement on the ground is presented as a function of jet height to diameter ratio. The impingement noise with the aircraft close to the ground was 14 to 17 dB greater than noise from a free jet. Results are compared with small-scale jet impingement data acquired elsewhere. The agreement between small-scale and full-scale noise increase in ground effect is fairly good except with the jet close to the ground. It is proposed that differences in the jet Reynolds numbers and the resultant character of the jets may be partially responsible for the disparity in the full-scale and small-scale jet impingement noise. The difference between single-jet impingement and multiple-jet impingement may also have been responsible for the small-scale and full-scale disagreement

Mercury cadmium telluride photodiode

High speed (Hg,Cd)Te photodiode detectors sensitive to 10.6 microns radiation with operating temperature range of 77 to 90

Calibration of the Ames Anechoic Facility. Phase 1: Short range plan

A calibration was made of the acoustic and aerodynamic characteristics of a small, open-jet wind tunnel in an anechoic room. The jet nozzle was 102 mm diameter and was operated subsonically. The anechoic-room dimensions were 7.6 m by 5.5 m by 3.4 m high (wedge tip to wedge tip). Noise contours in the chamber were determined by various jet speeds and exhaust collector positions. The optimum nozzle/collector separation from an acoustic standpoint was 2.1 m. Jet velocity profiles and turbulence levels were measured using pressure probes and hot wires. The jet was found to be symmetric, with no unusual characteristics. The turbulence measurements were hampered by oil mist contamination of the airflow

Electromagnetic response of a static vortex line in a type-II superconductor : a microscopic study

The electromagnetic response of a pinned Abrikosov fluxoid is examined in the framework of the Bogoliubov-de Gennes formalism. The matrix elements and the selection rules for both the single photon (emission - absorption) and two photon (Raman scattering) processes are obtained. The results reveal striking asymmetries: light absorption by quasiparticle pair creation or single quasiparticle scattering can occur only if the handedness of the incident radiation is opposite to that of the vortex core states. We show how these effects will lead to nonreciprocal circular birefringence, and also predict structure in the frequency dependence of conductivity and in the differential cross section of the Raman scattering.Comment: 14 pages (RevTex

Population-Based Rates of Revision of Primary Total Hip Arthroplasty: A Systematic Review

Background: Most research on failure leading to revision total hip arthroplasty (THA) is reported from single centers. We searched PubMed between January 2000 and August 2010 to identify population- or community-based studies evaluating ten-year revision risks. We report ten-year revision risk using the Kaplan-Meier method, stratifying by age and fixation technique. Results: Thirteen papers met the inclusion criteria. Cemented prostheses had Kaplan-Meier estimates of revision-free implant survival of ten years ranging from 88 % to 95%; uncemented prostheses had Kaplan-Meier estimates from 80 % to 85%. Estimates ranged from 72 % to 86 % in patients less than 60 years old and from 90 to 96 % in older patients. Conclusion: Data reported from national registries suggest revision risks of 5 to 20 % ten years following primary THA. Revision risks are lower in older THA recipients. Uncemented implants may have higher ten-year rates of revision, regardless of age

Systematic review of tonsil surgery quality registers and introduction of the Nordic Tonsil Surgery Register Collaboration

Surgical quality registers provide tools to measure and improve the outcome of surgery. International register collaboration creates an opportunity to assess and critically evaluate national practices, and increases the size of available datasets. Even though millions of yearly tonsillectomies and tonsillotomies are performed worldwide, clinical practices are variable and inconsistency of evidence regarding the best clinical practice exists. The need for quality improvement actions is evident. We aimed to systematically investigate the existing tonsil surgery quality registers found in the literature, and to provide a thorough presentation of the planned Nordic Tonsil Surgery Register Collaboration. A systematic literature search of MEDLINE and EMBASE databases (from January 1990 to December 2016) was conducted to identify registers, databases, quality improvement programs or comprehensive audit programs addressing tonsil surgery. We identified two active registers and three completed audit programs focusing on tonsil surgery quality registration. Recorded variables were fairly similar, but considerable variation in coverage, number of operations included and length of time period for inclusion was discovered. Considering tonsillectomies and tonsillotomies being among the most commonly performed surgical procedures in otorhinolaryngology, it is surprising that only two active registers could be identified. We present a Nordic Tonsil Surgery Register Collaboration-an international tonsil surgery quality register project aiming to provide accurate benchmarks and enhance the quality of tonsil surgery in Denmark, Finland, Norway and Sweden.Peer reviewe

The Harris hip score: Do ceiling effects limit its usefulness in orthopedics?: A systematic review

The Harris hip score (HHS), a disease-specific health status scale that is frequently used to measure the outcome of total hip arthroplasty, has never been validated properly. A questionnaire is suitable only when all 5 psychometric properties are of sufficient quality. We questioned the usefulness of the HHS by investigating its content validity. We performed a systematic review based on a literature search in PubMed, Embase, and the Cochrane Library for descriptive studies published in 2007. 54 studies (59 patient groups) met our criteria and were included in the data analysis. To determine the content validity, we calculated the ceiling effect (percentage) for each separate study and we pooled data to measure the weighted mean. A subanalysis of indications for THA was performed to differentiate the populations for which the HHS would be suitable and for which it would not. A ceiling effect of 15% or less was considered to be acceptable. Over half the studies (31/59) revealed unacceptable ceiling effects. Pooled data across the studies included (n = 6,667 patients) suggested ceiling effects of 20% (95%CI: 18-22). Ceiling effects were greater (32%, 95%CI:12-52) in those patients undergoing hip resurfacing arthroplasty. Although the Harris hip score is widely used in arthroplasty research on outcomes, ceiling effects are common and these severely limit its validity in this field of researc

Does parallel item content on WOMAC's Pain and Function Subscales limit its ability to detect change in functional status?

BACKGROUND: Although the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) is considered the leading outcome measure for patients with osteoarthritis of the lower extremity, recent work has challenged its factorial validity and the physical function subscale's ability to detect valid change when pain and function display different profiles of change. This study examined the etiology of the WOMAC's physical function subscale's limited ability to detect change in the presence of discordant changes for pain and function. We hypothesized that the duplication of some items on the WOMAC's pain and function subscales contributed to this shortcoming. METHODS: Two eight-item physical function scales were abstracted from the WOMAC's 17-item physical function subscale: one contained activities and themes that were duplicated on the pain subscale (SIMILAR-8); the other version avoided overlapping activities (DISSIMILAR-8). Factorial validity of the shortened measures was assessed on 310 patients awaiting hip or knee arthroplasty. The shortened measures' abilities to detect change were examined on a sample of 104 patients following primary hip or knee arthroplasty. The WOMAC and three performance measures that included activity specific pain assessments – 40 m walk test, stair test, and timed-up-and-go test – were administered preoperatively, within 16 days of hip or knee arthroplasty, and at an interval of greater than 20 days following the first post-surgical assessment. Standardized response means were used to quantify change. RESULTS: The SIMILAR-8 did not demonstrate factorial validity; however, the factorial structure of the DISSIMILAR-8 was supported. The time to complete the performance measures more than doubled between the preoperative and first postoperative assessments supporting the theory that lower extremity functional status diminished over this interval. The DISSIMILAR-8 detected this deterioration in functional status; however, no significant change was noted for the SIMILAR-8. The WOMAC pain scale demonstrated a slight reduction in pain and the performance specific pain measures did not reflect a change in pain. All measures showed substantial improvement over the second assessment interval. CONCLUSIONS: These findings support the hypothesis that activity overlap on the pain and function subscales plays a causal role in limiting the WOMAC physical function subscale's ability to detect change