Instant Continual Learning of Neural Radiance Fields

Neural radiance fields (NeRFs) have emerged as an effective method for novel-view synthesis and 3D scene reconstruction. However, conventional training methods require access to all training views during scene optimization. This assumption may be prohibitive in continual learning scenarios, where new data is acquired in a sequential manner and a continuous update of the NeRF is desired, as in automotive or remote sensing applications. When naively trained in such a continual setting, traditional scene representation frameworks suffer from catastrophic forgetting, where previously learned knowledge is corrupted after training on new data. Prior works in alleviating forgetting with NeRFs suffer from low reconstruction quality and high latency, making them impractical for real-world application. We propose a continual learning framework for training NeRFs that leverages replay-based methods combined with a hybrid explicit--implicit scene representation. Our method outperforms previous methods in reconstruction quality when trained in a continual setting, while having the additional benefit of being an order of magnitude faster.Comment: For project page please visit https://ryanpo.com/icngp

Investigation of factors affecting the accumulation of vinyl chloride in polyvinyl chloride piping used in drinking water distribution systems

Plastic piping made of polyvinyl chloride (PVC), and chlorinated PVC (CPVC), is being increasingly used for drinking water distribution lines. Given the formulation of the material from vinyl chloride (VC), there has been concern that the VC (a confirmed human carcinogen) can leach from the plastic piping into drinking water. PVC/CPVC pipe reactors in the laboratory and tap samples collected from consumers homes (n = 15) revealed vinyl chloride accumulation in the tens of ng/L range after a few days and hundreds of ng/L after two years. While these levels did not exceed the EPA’s maximum contaminant level (MCL) of 2 μg/L, many readings that simulated stagnation times in homes (overnight) exceeded the MCL-Goal of 0 μg/L. Considerable differences in VC levels were seen across different manufacturers, while aging and biofilm effects were generally small. Preliminary evidence suggests that VC may accumulate not only via chemical leaching from the plastic piping, but also as a disinfection byproduct (DBP) via a chlorine-dependent reaction. This is supported from studies with CPVC pipe reactors where chlorinated reactors accumulated more VC than dechlorinated reactors, copper pipe reactors that accumulated VC in chlorinated reactors and not in dechlorinated reactors, and field samples where VC levels were the same before and after flushing the lines where PVC/CPVC fittings were contributing. Free chlorine residual tests suggest that VC may be formed as a secondary, rather than primary, DBP. Further research and additional studies need to be conducted in order to elucidate reaction mechanisms and tease apart relative contributions of VC accumulation from PVC/CPVC piping and chlorine-dependent reactions

Partnership for the implementation of mental health policy in Nigeria: a case study of the Comprehensive Community Mental Health Programme in Benue State.

BACKGROUND: 71% of countries in the World Health Organisation's (WHO's) African Region have a stand-alone mental health policy or plan, but only 14% have fully implemented it. In Nigeria, integration of mental health into primary care has been a stumbling block to the implementation of the 1991 National Mental Health Policy, 2013 Policy on Mental Health Services Delivery and the National Mental, Neurological and Substance Use Programme and Action Plan. A partnership between public and private not-for-profits in Benue State, the Comprehensive Community Mental Health Programme (CCMHP) has successfully integrated mental health into primary care in alignment with the national mental health policy and the WHO's mental health Gap Action Programme Intervention Guide (mhGAP-IG). There is a need to document such examples in order to inform policy implementation in Nigeria and other low- and middle-income countries (LMICs). METHODS: We followed the Case Study Methodology to Monitor and Evaluate Community Mental Health Programmes in LMICs. Four field visits were conducted between 2013 and 2017 to document the first phase of activities of CCMHP, covering the period of January 2011 through June 2016. RESULTS: In its first phase, CCMHP trained 19 community psychiatric nurses and 48 community health extension workers in mhGAP-IG, establishing 45 new mental health clinics in primary care facilities across Benue, a state more populous than many countries. As a result, 13,785 clients (55% male, 45% female) were enrolled in mental health services either in primary care or in one of two pre-existing community-based rehabilitation facilities. Most are adults over age 18 (82.75%), and present to services with epilepsy (52.38%) or psychosis (38.41%). CONCLUSION: The case of CCMHP demonstrates it is possible to rapidly scale-up mental health services in line with national mental health policy using the mhGAP-IG, even in a challenging, low-resource setting. Multi-sectoral partnerships may help to overcome some of the barriers to successful integration of mental health into general healthcare by capitalising on the resources and expertise of both state and non-state actors. However, a difficult political context could threaten the sustainability of the programme if funder requirements force a rapid transition to full government ownership

Characterization of dislocation ensembles: measures and complexity

publishedVersionNon peer reviewe

State of the Art on Diffusion Models for Visual Computing

The field of visual computing is rapidly advancing due to the emergence of generative artificial intelligence (AI), which unlocks unprecedented capabilities for the generation, editing, and reconstruction of images, videos, and 3D scenes. In these domains, diffusion models are the generative AI architecture of choice. Within the last year alone, the literature on diffusion-based tools and applications has seen exponential growth and relevant papers are published across the computer graphics, computer vision, and AI communities with new works appearing daily on arXiv. This rapid growth of the field makes it difficult to keep up with all recent developments. The goal of this state-of-the-art report (STAR) is to introduce the basic mathematical concepts of diffusion models, implementation details and design choices of the popular Stable Diffusion model, as well as overview important aspects of these generative AI tools, including personalization, conditioning, inversion, among others. Moreover, we give a comprehensive overview of the rapidly growing literature on diffusion-based generation and editing, categorized by the type of generated medium, including 2D images, videos, 3D objects, locomotion, and 4D scenes. Finally, we discuss available datasets, metrics, open challenges, and social implications. This STAR provides an intuitive starting point to explore this exciting topic for researchers, artists, and practitioners alike

Brominated flame retardants in Canadian chicken egg yolks

Chicken eggs categorised as conventional, omega-3 enriched, free range and organic were collected at grading stations in three regions of Canada between 2005 and 2006. Free run eggs, which were only available for collection from two regions, were also sampled during this time frame. Egg yolks from each of these egg types (n = 162) were analysed to determine brominated flame retardant levels, specifically polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). PBDEs were detected in 100% of the 162 samples tested, while HBCD was observed in 85% of the egg yolks. Total PBDE concentrations in egg yolks ranged from 0.018 to 20.9 ng g−1 lipid (median = 3.03 ng g−1 lipid), with PBDE 209 identified as being the major contributor to ΣPBDE concentrations. In addition to PBDE 209, PBDE 99, 47, 100, 183 and 153 were important contributors to ΣPBDE concentrations. Total HBCD concentrations ranged from below the limit of detection to a maximum concentration of 71.9 ng g−1 lipid (median = 0.053 ng g−1 lipid). The α-isomer was the dominant contributor to ΣHBCD levels in Canadian egg yolks and was the most frequently detected HBCD isomer. ΣPBDE levels exhibited large differences in variability between combinations of region and type. ΣHBCD concentrations were not significantly different among regions, although differences were observed between the different types of egg yolks analysed in the present study