25 research outputs found
The Pioneer Anomaly
Radio-metric Doppler tracking data received from the Pioneer 10 and 11
spacecraft from heliocentric distances of 20-70 AU has consistently indicated
the presence of a small, anomalous, blue-shifted frequency drift uniformly
changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was
interpreted as a constant sunward deceleration of each particular spacecraft at
the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of
the Newton's gravitational inverse-square law has become known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. In this review, we
summarize the current knowledge of the physical properties of the anomaly and
the conditions that led to its detection and characterization. We review
various mechanisms proposed to explain the anomaly and discuss the current
state of efforts to determine its nature. A comprehensive new investigation of
the anomalous behavior of the two Pioneers has begun recently. The new efforts
rely on the much-extended set of radio-metric Doppler data for both spacecraft
in conjunction with the newly available complete record of their telemetry
files and a large archive of original project documentation. As the new study
is yet to report its findings, this review provides the necessary background
for the new results to appear in the near future. In particular, we provide a
significant amount of information on the design, operations and behavior of the
two Pioneers during their entire missions, including descriptions of various
data formats and techniques used for their navigation and radio-science data
analysis. As most of this information was recovered relatively recently, it was
not used in the previous studies of the Pioneer anomaly, but it is critical for
the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living
Reviews in Relativit
Patient preferences for emergency or planned hip fracture surgery: a cross-sectional study
Neck of femur fractures in the over 90s: a select group of patients who require prompt surgical intervention for optimal results
Time to death in a prospective cohort of 252 patients treated for fracture of the proximal femur in a major hospital in Portugal
Pressure Ulcers and Prolonged Hospital Stay in Hip Fracture Patients Affected by Time-to-Surgery
Effect of surgical delay on outcome in hip fracture patients: a retrospective multivariate analysis of 192 patients
Previous studies have not demonstrated consistent results on the effect of surgical delay on outcome. This study investigated the association between the delay to surgery and the development of postoperative complications, length of hospital stay (LOS) and one-year mortality. Patients that underwent surgery for a hip fracture in a two-year period were included in a retrospective study. Uni- and multivariate regression analysis was performed in 192 hip fracture patients. There was a trend towards fewer postoperative complications (P = 0.064; multivariate regression, MR) and shorter LOS (P = 0.088; MR) in patients with a delay of less than one day to surgery. No association between surgical delay and one-year mortality was found in the population as a whole (P = 0.632; univariate regression, UR). Delay to surgery beyond one day was associated with an increased risk of infectious complications (P = 0.004; MR). In ASA I and II class patients, operation beyond one day from admission was associated with an increased risk of one-year mortality (P = 0.03; MR) and more postoperative infectious complications (P = 0.02; MR). The trends towards fewer complications and shorter LOS suggest that early surgery (within one day from admission) is beneficial for hip fracture patients who are able to undergo an operation
Prospective study of surgical delay for hip fractures: impact of an orthogeriatrician and increased trauma capacity
Most health services in the United Kingdom provide unacceptable in-hospital care for hip fracture patients. We describe the impact on surgical delay following the introduction of an orthogeriatrician and the addition of one extra trauma list per week at our centre. Prospective data were collected on 101 consecutive patients followed by a second cohort of 105 patients. Mean time to surgery in cohorts 1 and 2 was 4.08 and 4.05 days, respectively (p = 0.71). Diagnosis of medical comorbidity increased with input from the orthogeriatrician from 69.7% to 74.2% (p = 0.24). Length of stay and mortality were comparable in the two groups. A full trauma list accounted for the most frequent orthopaedic delay, which decreased from 18.1% to 12.9% (p = 0.09). Increased recognition of medical comorbidity has financial implications for hospital remuneration. However, lack of orthopaedic provisions accounts for significant avoidable surgical delay requiring further investment if national standards are to be achieved