Approaching the motional ground state of a 10-kg object.

The motion of a mechanical object, even a human-sized object, should be governed by the rules of quantum mechanics. Coaxing them into a quantum state is, however, difficult because the thermal environment masks any quantum signature of the object's motion. The thermal environment also masks the effects of proposed modifications of quantum mechanics at large mass scales. We prepared the center-of-mass motion of a 10-kilogram mechanical oscillator in a state with an average phonon occupation of 10.8. The reduction in temperature, from room temperature to 77 nanokelvin, is commensurate with an 11 orders-of-magnitude suppression of quantum back-action by feedback and a 13 orders-of-magnitude increase in the mass of an object prepared close to its motional ground state. Our approach will enable the possibility of probing gravity on massive quantum systems.

Quantum-Enhanced Advanced LIGO Detectors in the Era of Gravitational-Wave Astronomy.

The Laser Interferometer Gravitational Wave Observatory (LIGO) has been directly detecting gravitational waves from compact binary mergers since 2015. We report on the first use of squeezed vacuum states in the direct measurement of gravitational waves with the Advanced LIGO H1 and L1 detectors. This achievement is the culmination of decades of research to implement squeezed states in gravitational-wave detectors. During the ongoing O3 observation run, squeezed states are improving the sensitivity of the LIGO interferometers to signals above 50 Hz by up to 3 dB, thereby increasing the expected detection rate by 40% (H1) and 50% (L1).

Squeezed vacuum phase control at 2 µm.

We demonstrate phase control for vacuum-squeezed light at a 2 µm wavelength, which is a necessary technology for proposed future gravitational wave observatories. The control scheme allowed examination of noise behavior at frequencies below 1 kHz and indicated that squeezing below this frequency was limited by dark noise and scattered light. We directly measure 3.9±0.2 dB of squeezing from 2 kHz to 80 kHz and 14.2±0.3 dB of antisqueezing relative to the shot noise level. The observed maximum level of squeezing is currently limited by photodetector quantum efficiency and laser instabilities at this new wavelength for squeezed light. Accounting for all losses, we conclude the generation of 11.3 dB of squeezing at the optical parametric oscillator.

Clinical course and prognostic factors across different musculoskeletal pain sites: A secondary analysis of individual patient data from randomised clinical trials.

BACKGROUND: Previous research has identified similar prognostic factors in patients with musculoskeletal (MSK) conditions regardless of pain presentation, generating opportunities for management based on prognosis rather than specific pain presentation. METHODS: Data from seven RCTs (2483 participants) evaluating a range of primary care interventions for different MSK pain conditions were used to investigate the course of symptoms and explore similarities and differences in predictors of outcome. The value of pain site for predicting changes in pain and function was investigated and compared with that of age, gender, social class, pain duration, widespread pain and level of anxiety/depression. RESULTS: Over the initial three months of follow-up, changes in mean pain intensity reflected an improvement, with little change occurring after this period. Participants with knee pain due to osteoarthritis (OA) showed poorer long-term outcome (mean difference in pain reduction at 12 months -1.85, 95% CI -2.12 to -1.57, compared to low back pain). Increasing age, manual work, longer pain duration, widespread pain and increasing anxiety/depression scores were significantly associated with poorer outcome regardless of pain site. Testing of interactions showed some variation between pain sites, particularly for knee OA, where age, manual work and pain duration were most strongly associated with outcome. CONCLUSIONS: Despite some differences in prognostic factors for trial participants with knee OA who were older and had more chronic conditions, similarity of outcome predictors across regional MSK pain sites provides evidence to support targeting of treatment based on prognostic factors rather than site of pain. SIGNIFICANCE: Individual patient data analysis of trials across different regional musculoskeletal pain sites was used to evaluate course and prognostic factors associated with pain and disability. Overall, similarity of outcome predictors across these different pain sites supports targeting of treatment based on prognostic factors rather than pain site alone.

Brief pain re-assessment provided more accurate prognosis than baseline information for low-back or shoulder pain.

BACKGROUND: Research investigating prognosis in musculoskeletal pain conditions has only been moderately successful in predicting which patients are unlikely to recover. Clinical decision making could potentially be improved by combining information taken at baseline and re-consultation. METHODS: Data from four prospective clinical cohorts of adults presenting to UK and Dutch primary care with low-back or shoulder pain was analysed, assessing long-term disability at 6 or 12 months and including baseline and 4-6 week assessments of pain. Baseline versus short-term assessments of pain, and previously validated multivariable prediction models versus repeat assessment, were compared to assess predictive performance of long-term disability outcome. A hypothetical clinical scenario was explored which made efficient use of both baseline and repeated assessment to identify patients likely to have a poor prognosis and decide on further treatment. RESULTS: Short-term repeat assessment of pain was better than short-term change or baseline score at predicting long-term disability improvement across all cohorts. Short-term repeat assessment of pain was only slightly more predictive of long-term recovery (c-statistics 0.78, 95% CI 0.74 to 0.83 and 0.75, 95% CI 0.69 to 0.82) than a multivariable baseline prognostic model in the two cohorts presenting such a model (c-statistics 0.71, 95% CI 0.67 to 0.76 and 0.72, 95% CI 0.66 to 0.78). Combining optimal prediction at baseline using a multivariable prognostic model with short-term repeat assessment of pain in those with uncertain prognosis in a hypothetical clinical scenario resulted in reduction in the number of patients with an uncertain probability of recovery, thereby reducing the instances where patients may be inappropriately referred or reassured. CONCLUSIONS: Incorporating short-term repeat assessment of pain into prognostic models could potentially optimise the clinical usefulness of prognostic information.

Applying causal mediation methods to clinical trial data: What can we learn about why our interventions (don't) work?

BACKGROUND: Many randomized controlled trials (RCTs) of psychosocial interventions for low back pain (LBP) have been found to have only small effects on disability outcomes. Investigations of the specific mechanisms that may lead to an improvement in outcome have therefore been called for. METHODS: We present an application of the causal inference approach to mediation analysis using the example of a cluster RCT in a primary care population with (sub)acute LBP randomized to either usual GP care (n = 171) or a minimal psychosocial intervention (n = 143). Mediation analysis explored the causal pathway between treatment allocation and disability at 3 months by considering pain catastrophizing, fear-avoidance beliefs, distress and receiving and following advice as potential mediators, all measured at 6 weeks. We have attempted to explain this approach to mediation analysis in a step-by-step manner to help clinical researchers apply this method more easily. RESULTS: In unadjusted mediation analyses, fear-avoidance beliefs were identified as a mediator of treatment on disability, with an indirect effect of -0.30 (95% CI: -0.86, -0.03), although this relationship was found to be non-significant after adjusting for age, gender and baseline scores. This finding supports the trial authors' hypothesis that while fear-avoidance beliefs are important, this intervention may not have targeted them strongly enough to lead to change. CONCLUSION: The use of mediation analysis to identify what factors may be part of the causal pathway between intervention and outcome, regardless of whether the intervention was successful, can provide useful information and insight into how to improve future interventions. SIGNIFICANCE: This study presents a step-by-step approach to mediation analysis using the causal inference framework to investigate why a psychosocial intervention for LBP was unsuccessful. Fear-avoidance beliefs were found to mediate the relationship between treatment and disability, although not when controlling for baseline scores.

Optomechanical design and construction of a vacuum-compatible optical parametric oscillator for generation of squeezed light.

With the recent detection of gravitational waves, non-classical light sources are likely to become an essential element of future detectors engaged in gravitational wave astronomy and cosmology. Operating a squeezed light source under high vacuum has the advantages of reducing optical losses and phase noise compared to techniques where the squeezed light is introduced from outside the vacuum. This will ultimately provide enhanced sensitivity for modern interferometric gravitational wave detectors that will soon become limited by quantum noise across much of the detection bandwidth. Here we describe the optomechanical design choices and construction techniques of a near monolithic glass optical parametric oscillator that has been operated under a vacuum of 10(-6) mbar. The optical parametric oscillator described here has been shown to produce 8.6 dB of quadrature squeezed light in the audio frequency band down to 10 Hz. This performance has been maintained for periods of around an hour and the system has been under vacuum continuously for several months without a degradation of this performance.

Causal mechanisms in the clinical course and treatment of back pain.

In recent years, there has been increasing interest in studying causal mechanisms in the development and treatment of back pain. The aim of this article is to provide an overview of our current understanding of causal mechanisms in the field. In the first section, we introduce key concepts and terminology. In the second section, we provide a brief synopsis of systematic reviews of mechanism studies relevant to the clinical course and treatment of back pain. In the third section, we reflect on the findings of our review to explain how understanding causal mechanisms can inform clinical practice and the implementation of best practice. In the final sections, we introduce contemporary methodological advances, highlight the key assumptions of these methods, and discuss future directions to advance the quality of mechanism-related studies in the back pain field.

Cause-specific noncardiac mortality in patients with congestive heart failure--a contemporary Canadian audit. Clinical Quality Improvement Network (CQIN) Investigators.

BACKGROUND: Noncardiac mortality in congestive heart failure (CHF) is substantial. OBJECTIVE: To define the specific causes of noncardiac mortality among hospitalized CHF patients. DESIGN: Retrospective medical record audit. SETTING: Three hospitals in British Columbia and Alberta, 1992-93. PATIENTS: A total of 2216 consecutive patients admitted with CHF. MAIN RESULTS: The overall mortality rate was 404 of 2216 (18%). Cause of death was cardiac in 290 of 404 (72%) patients, with an average age of 76 years. However, 114 of 404 (28%) deaths, in patients with an average age of 69 years, had noncardiac causes. Four causes accounted for almost 70%, of the noncardiac deaths: cancer (24%); pneumonia (16%); other pulmonary diseases, including embolism (15%); and cerebrovascular disease (11%). Renal disease (9%), gastrointestinal disorders (9%), non-pulmonic sepsis (7%), multiple system failure (5%) and trauma or surgical complications (4%) accounted for most of the remaining noncardiac deaths. CONCLUSIONS: Noncardiac causes produce a substantial proportion of deaths among elderly and sick CHF patients. As the survival of patients with CHF improves, the relative risk of noncardiac mortality in this population will likely increase. However, since hospitalized CHF patients so closely reflect their general population counterparts in terms of cause-specific mortality risk, the search for an ideal therapy might be viewed as a quixotic search for the cure of death.

Phosphorus deficiency in a dairy herd.

Phosphorus deficiency was diagnosed in a 90 cow seasonal supply dairy herd which showed low milk production, ill-thrift, infertility and osteophagia. Serum inorganic phosphorus and pasture phosphorus levels were low, pasture Ca:P ratios high and soil phosphorus levels very low; the soil phosphate retention value was 96%. The deficiency, which had probably existed for several years, was considered to be due to inadequate annual phosphate fertiliser applications on a high phosphate retaining soil. Phosphorus deficiency may have been exacerbated by the application of lime without phosphate several months before the onset of severe clinical disease. The finding of low sodium levels in pasture samples suggested that sodium deficiency may have co-existed and contributed to the clinical picture. Treatment, comprising bone flour dusting of pasture, water trough supplementation and phosphorus-containing injections, appeared to induce ovarian activity in anoestrous cows and suppress osteophagia, though controlled treatment trials were not performed. No improvement was noted in milk production or cow condition. Increased annual super-phosphate and reduced potassium applications were recommended, together with the monitoring of pasture and soil macro elements and serum phosphorus levels. A decision on whether to supplement with sodium would be based on the results of pasture monitoring, since a direct animal test is not currently available. It is suggested that phosphorus deficiency may not be uncommon in dairy herds in some North Island districts; based on the present case, the decline in New Zealand superphosphate quality in the 1970's and recently published data which has shown a high proportion of pasture phosphorus deficient sites in some North Island areas.