A thorough analysis of the key factors impacting on the performance of Brillouin distributed optical fiber sensors is presented. An analytical expression is derived to estimate the error on the ...determination of the Brillouin peak gain frequency, based for the first time on real experimental conditions. This expression is experimentally validated, and describes how this frequency uncertainty depends on measurement parameters, such as Brillouin gain linewidth, frequency scanning step and signal-to-noise ratio. Based on the model leading to this expression and considering the limitations imposed by nonlinear effects and pump depletion, a figure-of-merit is proposed to fairly compare the performance of Brillouin distributed sensing systems. This figure-of-merit offers to the research community and to potential users the possibility to evaluate with an objective metric the real performance gain resulting from any proposed configuration.
Background
This is the third update of a review that was originally published in the Cochrane Library in 2002, Issue 2. People with cancer, their families and carers have a high prevalence of ...psychological stress, which may be minimised by effective communication and support from their attending healthcare professionals (HCPs). Research suggests communication skills do not reliably improve with experience, therefore, considerable effort is dedicated to courses that may improve communication skills for HCPs involved in cancer care. A variety of communication skills training (CST) courses are in practice. We conducted this review to determine whether CST works and which types of CST, if any, are the most effective.
Objectives
To assess whether communication skills training is effective in changing behaviour of HCPs working in cancer care and in improving HCP well‐being, patient health status and satisfaction.
Search methods
For this update, we searched the following electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 4), MEDLINE via Ovid, Embase via Ovid, PsycInfo and CINAHL up to May 2018. In addition, we searched the US National Library of Medicine Clinical Trial Registry and handsearched the reference lists of relevant articles and conference proceedings for additional studies.
Selection criteria
The original review was a narrative review that included randomised controlled trials (RCTs) and controlled before‐and‐after studies. In updated versions, we limited our criteria to RCTs evaluating CST compared with no CST or other CST in HCPs working in cancer care. Primary outcomes were changes in HCP communication skills measured in interactions with real or simulated people with cancer or both, using objective scales. We excluded studies whose focus was communication skills in encounters related to informed consent for research.
Data collection and analysis
Two review authors independently assessed trials and extracted data to a pre‐designed data collection form. We pooled data using the random‐effects method. For continuous data, we used standardised mean differences (SMDs).
Main results
We included 17 RCTs conducted mainly in outpatient settings. Eleven trials compared CST with no CST intervention; three trials compared the effect of a follow‐up CST intervention after initial CST training; two trials compared the effect of CST and patient coaching; and one trial compared two types of CST. The types of CST courses evaluated in these trials were diverse. Study participants included oncologists, residents, other doctors, nurses and a mixed team of HCPs. Overall, 1240 HCPs participated (612 doctors including 151 residents, 532 nurses, and 96 mixed HCPs).
Ten trials contributed data to the meta‐analyses. HCPs in the intervention groups were more likely to use open questions in the post‐intervention interviews than the control group (SMD 0.25, 95% CI 0.02 to 0.48; P = 0.03, I² = 62%; 5 studies, 796 participant interviews; very low‐certainty evidence); more likely to show empathy towards their patients (SMD 0.18, 95% CI 0.05 to 0.32; P = 0.008, I² = 0%; 6 studies, 844 participant interviews; moderate‐certainty evidence), and less likely to give facts only (SMD ‐0.26, 95% CI ‐0.51 to ‐0.01; P = 0.05, I² = 68%; 5 studies, 780 participant interviews; low‐certainty evidence). Evidence suggesting no difference between CST and no CST on eliciting patient concerns and providing appropriate information was of a moderate‐certainty. There was no evidence of differences in the other HCP communication skills, including clarifying and/or summarising information, and negotiation. Doctors and nurses did not perform differently for any HCP outcomes.
There were no differences between the groups with regard to HCP 'burnout' (low‐certainty evidence) nor with regard to patient satisfaction or patient perception of the HCPs communication skills (very low‐certainty evidence). Out of the 17 included RCTs 15 were considered to be at a low risk of overall bias.
Authors' conclusions
Various CST courses appear to be effective in improving HCP communication skills related to supportive skills and to help HCPs to be less likely to give facts only without individualising their responses to the patient's emotions or offering support. We were unable to determine whether the effects of CST are sustained over time, whether consolidation sessions are necessary, and which types of CST programs are most likely to work. We found no evidence to support a beneficial effect of CST on HCP 'burnout', the mental or physical health and satisfaction of people with cancer.
Abstract
Distributed acoustic sensors (DAS) can monitor mechanical vibrations along thousands independent locations using an optical fibre. The measured acoustic waveform highly varies along the ...sensing fibre due to the intrinsic uneven DAS longitudinal response and distortions originated during mechanical wave propagation. Here, we propose a fully blind method based on near-field acoustic array processing that considers the nonuniform response of DAS channels and can be used with any optical fibre positioning geometry having angular diversity. With no source and fibre location information, the method can reduce signal distortions and provide relevant signal-to-noise ratio enhancement through sparse beamforming spatial filtering. The method also allows the localisation of the two-dimensional spatial coordinates of acoustic sources, requiring no specific fibre installation design. The method offers distributed analysis capabilities of the entire acoustic field outside the sensing fibre, enabling DAS systems to characterise vibration sources placed in areas far from the optical fibre.
A theoretical and experimental study on the response of Brillouin scattering in multi-core optical fibers (MCF) under different curving conditions is presented. Results demonstrate that the Brillouin ...frequency shift of the off-center cores in MCF is highly bending-dependent, showing a linear dependence on the fiber curvature. This feature is here exploited to develop a new kind of distributed optical fiber sensor, which provides measurements of a distributed profile mapping the longitudinal fiber shape. Using conventional Brillouin optical time-domain analysis with differential pulse-width pairs, fully distributed shape sensing along a 1 km-long MCF is practically demonstrated. Experimental results show a very good agreement with the theoretically expected behavior deduced from the dependence of the Brillouin frequency on the strain induced by the fiber bending over a given core. The analysis and results presented in this paper constitute the first demonstration of distributed bending sensing, providing the cornerstone to further develop it into a fully distributed three-dimensional shape sensor.
The distributed fibre sensing technology based on backward stimulated Brillouin scattering (BSBS) is experiencing a rapid development. However, all reported implementations of distributed Brillouin ...fibre sensors until today are restricted to detecting physical parameters inside the fibre core. On the contrary, forward stimulated Brillouin scattering (FSBS), due to its resonating transverse acoustic waves, is being studied recently to facilitate innovative detections in the fibre surroundings, opening sensing domains that are impossible with BSBS. Nevertheless, due to the co-propagating behaviour of the pump and scattered lights, it is a challenge to position-resolve FSBS information along a fibre. Here we show a distributed FSBS analysis based on recovering the FSBS induced phase change of the propagating light waves. A spatial resolution of 15 m is achieved over a length of 730 m and the local acoustic impedances of water and ethanol in a 30 m-long uncoated fibre segment are measured, agreeing well with the standard values.
Many research questions in sensory neuroscience involve determining whether the neural representation of a stimulus property is invariant or specific to a particular stimulus context (e.g., Is object ...representation invariant to translation? Is the representation of a face feature specific to the context of other face features?). Between these two extremes, representations may also be context-tolerant or context-sensitive. Most neuroimaging studies have used operational tests in which a target property is inferred from a significant test against the null hypothesis of the opposite property. For example, the popular cross-classification test concludes that representations are invariant or tolerant when the null hypothesis of specificity is rejected. A recently developed neurocomputational theory suggests two insights regarding such tests. First, tests against the null of context-specificity, and for the alternative of context-invariance, are prone to false positives due to the way in which the underlying neural representations are transformed into indirect measurements in neuroimaging studies. Second, jointly performing tests against the nulls of invariance and specificity allows one to reach more precise and valid conclusions about the underlying representations, particularly when the null of invariance is tested using the fine-grained information from classifier decision variables rather than only accuracies (i.e., using the decoding separability test). Here, we provide empirical and computational evidence supporting both of these theoretical insights. In our empirical study, we use encoding of orientation and spatial position in primary visual cortex as a case study, as previous research has established that these properties are encoded in a context-sensitive way. Using fMRI decoding, we show that the cross-classification test produces false-positive conclusions of invariance, but that more valid conclusions can be reached by jointly performing tests against the null of invariance. The results of two simulations further support both of these conclusions. We conclude that more valid inferences about invariance or specificity of neural representations can be reached by jointly testing against both hypotheses, and using neurocomputational theory to guide the interpretation of results.
Distributed optical fibre sensors possess the unique capability of measuring the spatial and temporal map of environmental quantities that can be of great interest for several field applications. ...Although existing methods for performance enhancement have enabled important progresses in the field, they do not take full advantage of all information present in the measured data, still giving room for substantial improvement over the state-of-the-art. Here we propose and experimentally demonstrate an approach for performance enhancement that exploits the high level of similitude and redundancy contained on the multidimensional information measured by distributed fibre sensors. Exploiting conventional image and video processing, an unprecedented boost in signal-to-noise ratio and measurement contrast is experimentally demonstrated. The method can be applied to any white-noise-limited distributed fibre sensor and can remarkably provide a 100-fold improvement in the sensor performance with no hardware modification.
A method based on coherent Rayleigh scattering distinctly evaluating temperature and strain is proposed and experimentally demonstrated for distributed optical fiber sensing. Combining conventional ...phase-sensitive optical time-domain domain reflectometry (ϕOTDR) and ϕOTDR-based birefringence measurements, independent distributed temperature and strain profiles are obtained along a polarization-maintaining fiber. A theoretical analysis, supported by experimental data, indicates that the proposed system for temperature-strain discrimination is intrinsically better conditioned than an equivalent existing approach that combines classical Brillouin sensing with Brillouin dynamic gratings. This is due to the higher sensitivity of coherent Rayleigh scatting compared to Brillouin scattering, thus offering better performance and lower temperature-strain uncertainties in the discrimination. Compared to the Brillouin-based approach, the ϕOTDR-based system here proposed requires access to only one fiber-end, and a much simpler experimental layout. Experimental results validate the full discrimination of temperature and strain along a 100 m-long elliptical-core polarization-maintaining fiber with measurement uncertainties of ~40 mK and ~0.5 με, respectively. These values agree very well with the theoretically expected measurand resolutions.
Distributed fiber sensing possesses the unique ability to measure the distributed profile of an environmental quantity along many tens of kilometers with spatial resolutions in the meter or even ...centimeter scale. This feature enables distributed sensors to provide a large number of resolved points using a single optical fiber. However, in current systems, this number has remained constrained to a few hundreds of thousands due to the finite signal-to-noise ratio (SNR) of the measurements, which imposes significant challenges in the development of more performing sensors. Here, we propose and experimentally demonstrate an ultimately optimized distributed fiber sensor capable of resolving 2100000 independent points, which corresponds to a one-order-of-magnitude improvement compared to the state-of-the-art. Using a Brillouin distributed fiber sensor based on phase-modulation correlation-domain analysis combined with temporal gating of the pump and time-domain acquisition, a spatial resolution of 8.3 mm is demonstrated over a distance of 17.5 km. The sensor design addresses the most relevant factors impacting the SNR and the performance of medium-to-long range sensors as well as of sub-meter spatial resolution schemes. This step record in the number of resolved points could be reached due to two theoretical models proposed and experimentally validated in this study: one model describes the spatial resolution of the system and its relation with the sampling interval, and the other describes the amplitude response of the sensor, providing an accurate estimation of the SNR of the measurements.
Background: Patients with metabolic syndrome (MS) have above-average risk of developing atherosclerosis and cardiovascular disease. Inflammation plays a key role in the development of ...atherosclerosis. High levels of the acute phase reactants C-reactive protein (CRP) and ferritin have been reported to correlate with various components of MS. Patients and methods: The serum CRP, ferritin, glucose, insulin, triglycerides, HDL-cholesterol and total cholesterol concentrations of 598 obese or overweight patients were determined, together with relevant anthropometric parameters. Insulin resistance was evaluated by the HOMA method. MS was diagnosed using the ATP III criteria. Results: CRP levels were higher among patients with central obesity than in those without (5.8 vs 3.9 mg/l; P=0.003), and higher among those with fasting plasma glucose concentrations >or= 110 mg/dl than in those with lower concentrations (7.4 vs 4.1 mg/l; P=0.01). Serum ferritin levels were higher among patients with triglyceride concentrations >or= 150 mg/dl than in those with lower levels (76.8 vs 40.1 ng/ml; P<0.001), and higher among those with fasting plasma glucose concentrations >or= 110 mg/dl than in those with lower concentrations (75.7 vs 41.7 ng/ml; P=0.005). The number of MS criteria that were satisfied increased with CRP and ferritin levels. Patients with insulin resistance also had higher CRP and ferritin levels than those without, 7.3 vs 4.3 mg/l for CRP (P=0.032) and 124.5 vs 80.1 ng/ml for ferritin (P<0.001). Conclusions: MS and insulin resistance are associated with elevated serum CRP and ferritin. Evaluation of subclinical chronic inflammation in patients with MS and/or insulin resistance by determination of these markers might aid in their evaluation as candidates for aggressive intervention against cardiovascular risk factors.
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