644 research outputs found
Chromatic Illumination Discrimination Ability Reveals that Human Colour Constancy Is Optimised for Blue Daylight Illuminations
The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow) and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K), all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed
The implausibility of âusual careâ in an open system: sedation and weaning practices in Paediatric Intensive Care Units (PICUs) in the United Kingdom (UK)
Background: The power of the randomised controlled trial depends upon its capacity to operate in a closed
system whereby the intervention is the only causal force acting upon the experimental group and absent in the
control group, permitting a valid assessment of intervention efficacy. Conversely, clinical arenas are open systems
where factors relating to context, resources, interpretation and actions of individuals will affect implementation and
effectiveness of interventions. Consequently, the comparator (usual care) can be difficult to define and variable in
multi-centre trials. Hence outcomes cannot be understood without considering usual care and factors that may
affect implementation and impact on the intervention.
Methods: Using a fieldwork approach, we describe PICU context, âusualâ practice in sedation and weaning from
mechanical ventilation, and factors affecting implementation prior to designing a trial involving a sedation and
ventilation weaning intervention. We collected data from 23 UK PICUs between June and November 2014 using
observation, individual and multi-disciplinary group interviews with staff.
Results: Pain and sedation practices were broadly similar in terms of drug usage and assessment tools. Sedation
protocols linking assessment to appropriate titration of sedatives and sedation holds were rarely used (9 % and 4 %
of PICUs respectively). Ventilator weaning was primarily a medical-led process with 39 % of PICUs engaging senior
nurses in the process: weaning protocols were rarely used (9 % of PICUs). Weaning methods were variably based
on clinician preference. No formal criteria or use of spontaneous breathing trials were used to test weaning
readiness. Seventeen PICUs (74 %) had prior engagement in multi-centre trials, but limited research nurse
availability. Barriers to previous trial implementation were intervention complexity, lack of belief in the evidence and
inadequate training. Facilitating factors were senior staff buy-in and dedicated research nurse provision.
Conclusions: We examined and identified contextual and organisational factors that may impact on the
implementation of our intervention. We found usual practice relating to sedation, analgesia and ventilator weaning
broadly similar, yet distinctively different from our proposed intervention, providing assurance in our ability to
evaluate intervention effects. The data will enable us to develop an implementation plan; considering these factors
we can more fully understand their impact on study outcomes
Higgsing M2 to D2 with gravity: N=6 chiral supergravity from topologically gauged ABJM theory
We present the higgsing of three-dimensional N=6 superconformal ABJM type
theories coupled to conformal supergravity, so called topologically gauged ABJM
theory, thus providing a gravitational extension of previous work on the
relation between N M2 and N D2-branes. The resulting N=6 supergravity theory
appears at a chiral point similar to that of three-dimensional chiral gravity
introduced recently by Li, Song and Strominger, but with the opposite sign for
the Ricci scalar term in the lagrangian. We identify the supersymmetry in the
broken phase as a particular linear combination of the supersymmetry and
special conformal supersymmetry in the original topologically gauged ABJM
theory. We also discuss the higgsing procedure in detail paying special
attention to the role played by the U(1) factors in the original ABJM model and
the U(1) introduced in the topological gauging.Comment: 53 pages, Late
Exploring the theories, determinants and policy-options of street vending: a demand-side approach
Street vending has been a common feature of urban centres for several decades, with a relatively high proportion of developing countriesâ populations depending on it for employment, income or survival. Taking a supply-side approach, studies have shown that urban plannersâ responses to street vending have followed the modernism theory. In this paper, we take a demand-side (buyer-focused) approach to studying street vending, which to date has received little attention from the academic community. Employing data from Lagos state, Nigeria, we report four explanations underpinning the demand-side of street vending: formal economy failures, social/redistributive, financial gains, and multifeature. These are, in turn, explained by individualsâ marital status, level of education, and perception. Our findings highlight the need for urban planners to embrace pragmatic policies in addressing these demand-side drivers of street vending and use of urban space, rather than criminalising its actors
Long-term outcome of patients with multiple myeloma after autologous hematopoietic cell transplantation and nonmyeloablative allografting
Rituximab in B-Cell Hematologic Malignancies: A Review of 20 Years of Clinical Experience
Rituximab is a human/murine, chimeric anti-CD20 monoclonal antibody with established efficacy, and a favorable and well-defined safety profile in patients with various CD20-expressing lymphoid malignancies, including indolent and aggressive forms of B-cell non-Hodgkin lymphoma. Since its first approval 20 years ago, intravenously administered rituximab has revolutionized the treatment of B-cell malignancies and has become a standard component of care for follicular lymphoma, diffuse large B-cell lymphoma, chronic lymphocytic leukemia, and mantle cell lymphoma. For all of these diseases, clinical trials have demonstrated that rituximab not only prolongs the time to disease progression but also extends overall survival. Efficacy benefits have also been shown in patients with marginal zone lymphoma and in more aggressive diseases such as Burkitt lymphoma. Although the proven clinical efficacy and success of rituximab has led to the development of other anti-CD20 monoclonal antibodies in recent years (e.g., obinutuzumab, ofatumumab, veltuzumab, and ocrelizumab), rituximab is likely to maintain a position within the therapeutic armamentarium because it is well established with a long history of successful clinical use. Furthermore, a subcutaneous formulation of the drug has been approved both in the EU and in the USA for the treatment of B-cell malignancies. Using the wealth of data published on rituximab during the last two decades, we review the preclinical development of rituximab and the clinical experience gained in the treatment of hematologic B-cell malignancies, with a focus on the well-established intravenous route of administration. This article is a companion paper to A. Davies, et al., which is also published in this issue
Propagation of an Earth-directed coronal mass ejection in three dimensions
Solar coronal mass ejections (CMEs) are the most significant drivers of
adverse space weather at Earth, but the physics governing their propagation
through the heliosphere is not well understood. While stereoscopic imaging of
CMEs with the Solar Terrestrial Relations Observatory (STEREO) has provided
some insight into their three-dimensional (3D) propagation, the mechanisms
governing their evolution remain unclear due to difficulties in reconstructing
their true 3D structure. Here we use a new elliptical tie-pointing technique to
reconstruct a full CME front in 3D, enabling us to quantify its deflected
trajectory from high latitudes along the ecliptic, and measure its increasing
angular width and propagation from 2-46 solar radii (approximately 0.2 AU).
Beyond 7 solar radii, we show that its motion is determined by an aerodynamic
drag in the solar wind and, using our reconstruction as input for a 3D
magnetohydrodynamic simulation, we determine an accurate arrival time at the
Lagrangian L1 point near Earth.Comment: 5 figures, 2 supplementary movie
Characterization of lymphocyte populations in nonspecific interstitial pneumonia*
STUDY OBJECTIVES: Nonspecific interstitial pneumonia (NSIP) has been identified as a distinct entity with a more favorable prognosis and better response to immunosuppressive therapies than usual interstitial pneumonia (UIP). However the inflammatory profile of NSIP has not been characterized. DESIGN: Using immunohistochemistry techniques on open lung biopsy specimens, the infiltrate in NSIP was characterized in terms of T and B cells, and macrophages, and the T cell population further identified as either CD4 (helper) or CD8 (suppressor-cytotoxic) T cells. The extent of Th1 and Th2 cytokine producing cells was determined and compared to specimens from patients with UIP. RESULTS: In ten NSIP tissue samples 41.4 ± 4% of mononuclear cells expressed CD3, 24.7 ± 1.8% CD4, 19.1 ± 2% CD8, 27.4 ± 3.9% CD20, and 14.3 ± 1.6% had CD68 expression. Mononuclear cells expressed INFγ 21.9 ± 1.9% of the time and IL-4 in 3.0 ± 1%. In contrast, biopsies from eight patients with UIP demonstrated substantially less cellular staining for either cytokine (INFγ; 4.6 ± 1.7% and IL-4; 0.6 ± 0.3%). Significant populations of CD20 positive B-cells were also identified. CONCLUSION: The lymphocytic infiltrate in NSIP is characterized by an elevated CD4/CD8 T-cell ratio, and is predominantly of Th1 type, with additional populations rich in B-cells. Such features are consistent with the favorable clinical course observed in patients with NSIP compared to UIP
Retroacetabular osteolytic lesions behind well-fixed prosthetic cups: pilot study of bearings-retaining surgery
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