2,127 research outputs found
Self-supervised learning for transferable representations
Machine learning has undeniably achieved remarkable advances thanks to large labelled datasets and supervised learning. However, this progress is constrained by the labour-intensive annotation process. It is not feasible to generate extensive labelled datasets for every problem we aim to address. Consequently, there has been a notable shift in recent times toward approaches that solely leverage raw data. Among these, self-supervised learning has emerged as a particularly powerful approach, offering scalability to massive datasets and showcasing considerable potential for effective knowledge transfer. This thesis investigates self-supervised representation learning with a strong focus on computer vision applications. We provide a comprehensive survey of self-supervised methods across various modalities, introducing a taxonomy that categorises them into four distinct families while also highlighting practical considerations for real-world implementation. Our focus thenceforth is on the computer vision modality, where we perform a comprehensive benchmark evaluation of state-of-the-art self supervised models against many diverse downstream transfer tasks. Our findings reveal that self-supervised models often outperform supervised learning across a spectrum of tasks, albeit with correlations weakening as tasks transition beyond classification, particularly for datasets with distribution shifts. Digging deeper, we investigate the influence of data augmentation on the transferability of contrastive learners, uncovering a trade-off between spatial and appearance-based invariances that generalise to real-world transformations. This begins to explain the differing empirical performances achieved by self-supervised learners on different downstream tasks, and it showcases the advantages of specialised representations produced with tailored augmentation. Finally, we introduce a novel self-supervised pre-training algorithm for object detection, aligning pre-training with downstream architecture and objectives, leading to reduced localisation errors and improved label efficiency. In conclusion, this thesis contributes a comprehensive understanding of self-supervised representation learning and its role in enabling effective transfer across computer vision tasks
LIPIcs, Volume 251, ITCS 2023, Complete Volume
LIPIcs, Volume 251, ITCS 2023, Complete Volum
Local and systemic factors affecting the outcome of endodontic therapy
Abstract
Aim: The aim of the present study was to investigate and correlate the prevalence of Enterococcus faecalis in saliva and in root canals with different pulpal and periapical conditions.
Methodology: Sixty-seven patients were divided into five groups based on pulpal and periapical tissue status: healthy vital teeth (HVT), healthy treated teeth without lesion (HTT), irreversible pulpitis (IP), necrosis (N), and post-treatment apical periodontitis (PTAP). Saliva, rubber dam, sterility control and pre-treatment root canal samples were collected and microbiologically processed by culture method. Phylogenetic relationship of E. faecalis isolates collected from root canals and saliva were investigated by whole genome sequencing. Fisher's exact test was used to correlate the presence of E. faecalis in root canals or saliva with clinical and/or radiographic findings. Linear/ logistic regression analyses were performed to establish the relationship between the presence of E. faecalis in root canals, saliva, and the status of periapical tissues.
Results: E. faecalis was found in 18 root canal and saliva samples. E. faecalis root canal isolates were recovered with the highest frequency from post-treatment apical periodontitis. The occurrence of E. faecalis in saliva was strongly associated with its detection in the root canals (P < 0.001). The pretreatment presence of E. faecalis in root canals was associated with significantly higher odds of having periapical lesions (OR=11.03; 95% CI, 1.27-95.70; p < 0.05;). Saliva and canal isolates from the same patient were highly correlated at the phylogenetic level (J>0.95).
Conclusion: This pilot study confirms the role of E. faecalis in developing peri-radicular lesions in secondary endodontic infections and suggests that saliva could be the main source of infection. Further studies are needed to investigate the exact origin of this bacteria and its true role in the pathogenesis of secondary/persistent endodontic infections
Meditative textual practices in England, 1661 – 1678
This thesis examines late seventeenth-century meditation as a textual practice in manuscript and print. It considers textual meditations, prayers, scriptural paraphrases, letters, memoirs, and verse, which appear in miscellanies in the period of the Cavalier Parliament, 1661 – 1678. It argues that texts were essential to meditative practice, and these texts were composed either for the practitioner or with distinct readerships in mind. Therefore the project examines the complex and shifting triad of writer, reader, and text in each instance. In addition, it shows how notions of completion, privacy, publication, literariness, and singular authorship are not fully compatible with the iterativity of the textual practices associated with meditation.
The study considers five meditative writers, found across social and confessional spectra: Katherine Austen, John Flavel, Elizabeth Delaval, Susanna Hopton, and Thomas Traherne. Each writer collates and composes texts – originated by themselves and others – into their miscellanies; and – often over long periods of time – edits, amends, or repurposes these texts according to individual circumstance. The writers deploy diverse devotional practices and textual genres including emblem, romantic fiction, and essay. Each chapter shows how differently these writers realise the general pattern described by the thesis
The thesis offers a new appreciation of the diversity of meditative practices and the textual practices associated with them. It challenges earlier perceptions of meditation as an isolated, private, devotional practice, and of meditative texts as a separate literary product of meditative thought. The thesis describes meditation as a textual habit of thought, and a rich source of knowledge, which underpinned, theological, mercantile, social, and philosophical thought. In addition, the thesis demonstrates the value of interpreting meditative texts in their material, textual, biographical, and cultural contexts, and offers a reassessment of the critical and contemporary values placed on verse and prose forms in devotional writing
(b2023 to 2014) The UNBELIEVABLE similarities between the ideas of some people (2006-2016) and my ideas (2002-2008) in physics (quantum mechanics, cosmology), cognitive neuroscience, philosophy of mind, and philosophy (this manuscript would require a REVOLUTION in international academy environment!)
(b2023 to 2014) The UNBELIEVABLE similarities between the ideas of some people (2006-2016) and my ideas (2002-2008) in physics (quantum mechanics, cosmology), cognitive neuroscience, philosophy of mind, and philosophy (this manuscript would require a REVOLUTION in international academy environment!
The Saqqara Necropolis through the New Kingdom: Biography of an Ancient Egyptian Cultural Landscape
This book is the first comprehensive monographic treatment of the New Kingdom (1539–1078 BCE) necropolis at Saqqara, the burial ground of the ancient Egyptian city of Memphis, and addresses questions fundamental to understanding the site’s development through time. For example, why were certain areas of the necropolis selected for burial in certain time periods; what were the tombs’ spatial relations to contemporaneous and older monuments; and what effect did earlier structures have on the positioning of tombs and structuring of the necropolis in later times? This study adopts landscape biography as a conceptual tool to study the long-time interaction between people and landscapes.NWO276-30-016Middle Eastern Studie
Behavior quantification as the missing link between fields: Tools for digital psychiatry and their role in the future of neurobiology
The great behavioral heterogeneity observed between individuals with the same
psychiatric disorder and even within one individual over time complicates both
clinical practice and biomedical research. However, modern technologies are an
exciting opportunity to improve behavioral characterization. Existing
psychiatry methods that are qualitative or unscalable, such as patient surveys
or clinical interviews, can now be collected at a greater capacity and analyzed
to produce new quantitative measures. Furthermore, recent capabilities for
continuous collection of passive sensor streams, such as phone GPS or
smartwatch accelerometer, open avenues of novel questioning that were
previously entirely unrealistic. Their temporally dense nature enables a
cohesive study of real-time neural and behavioral signals.
To develop comprehensive neurobiological models of psychiatric disease, it
will be critical to first develop strong methods for behavioral quantification.
There is huge potential in what can theoretically be captured by current
technologies, but this in itself presents a large computational challenge --
one that will necessitate new data processing tools, new machine learning
techniques, and ultimately a shift in how interdisciplinary work is conducted.
In my thesis, I detail research projects that take different perspectives on
digital psychiatry, subsequently tying ideas together with a concluding
discussion on the future of the field. I also provide software infrastructure
where relevant, with extensive documentation.
Major contributions include scientific arguments and proof of concept results
for daily free-form audio journals as an underappreciated psychiatry research
datatype, as well as novel stability theorems and pilot empirical success for a
proposed multi-area recurrent neural network architecture.Comment: PhD thesis cop
Men, Women, and Italians: The Masquerade of Narrative and Identity in Richardson\u27s \u3ci\u3eSir Charles Grandison\u3c/i\u3e
The chaotic masquerades that proliferated during the British long eighteenth century punctuated the period’s preoccupation with order and categorization. The identity categories that the masquerade disrupted, the novel reinforced, or perhaps even created. It was in the middle of this period, in the political center of Britain, that Samuel Richardson published his third and final novel, The History of Sir Charles Grandison (1753), a novel which centers England and was also centered by England, a national treasure entangled in literary and cultural history. Tracing the nexus of gender and nationalism in Grandison then becomes important given the novel’s active entanglement in the debates that birthed the modern individual and the “private” sphere. In part because of its historical positioning, Grandison serves as a catalog of the period’s identity debates. The dramatis personae divides characters into “men,” “women,” and “Italians,” but at the same time that the structure attempts to relegate characters to their respective narrative and social spaces, they resist, for the paratext provides framing that the narrative subverts. In the dramatis personae, characters dress for a masquerade; the text, however, rejects these superficial trimmings, stripping the characters, structure, and plot of their masks. The blurring between man and woman, Briton and Italian, realism and romance create crises of category, and so Grandison’s narrative uses disrupted generic modes and changeable character masks to imagine a stronger community not in spite of but due to the permeable boundaries of narrative, nation, gender, and even the human body itself.
Literary conventions speak through the text, and in asserting arbitrary divisions remind us that boundaries in general are masquerades, that even genre itself simply apes order, protecting against the chaos that would unsettle what we believe about identity, community, and creation. The study of Grandison, a literary model for questioning binaries of all kinds, contributes to the field of cultural studies by providing a long scope of the identity debates which entangle the twenty-first century, and by suggesting that it is through the imaginative potential of fiction that we may begin to disentangle ourselves
Domes and Crosses: Exploiting synergies in two methodologies for biaxial tensile testing of membrane tissues
Biaxial tensile testing is the preferred method for mechanically testing membranous tissue as it can capture the tissue load response more holistically than uniaxial methods. There are two dominant approaches within the field of biaxial tensile testing: planar and bulge. Both methods can induce a state of biaxial tension within a specimen and both have their advantages and disadvantages. Bulge testing has the benefit of imposing a simple boundary condition on the tissue, making it quick and easy to set up. Planar Biaxial Tensile (PBT) testing is very sensitive to specimen preparation and requires non-trivial gripping systems. Some knowledge of the direction of maximum stiffness, prior to specimen mounting, is necessary for PBT to yield useful data. However, literature suggests that PBT is the more rigorous of the methods when it comes to collecting data to fully characterise a material model for membrane tissues. This study used the ease of bulge testing to determine the mean fibre axis of the tissue which informed the angle of PBT specimen excision. This was a rapid, non-destructive and creative method to avoid otherwise highly expensive imaging approaches to determine mean fibre direction. Further work was also done to develop a method of accurately determining specimen thickness for very thin tissues using a creative histological technique. By using a block of cutting medium to shape the membrane during processing steps, all four of the loaded edges of the tissue could be sectioned simultaneously for thickness measurement. Finally, the study served to develop a membrane tissue test protocol for further research using the in-house built biaxial tensile machines
The Saqqara Necropolis through the New Kingdom: Biography of an Ancient Egyptian Cultural Landscape
peer reviewedThis book is the first comprehensive monographic treatment of the New Kingdom (1539–1078 BCE) necropolis at Saqqara, the burial ground of the ancient Egyptian city of Memphis, and addresses questions fundamental to understanding the site’s development through time. For example, why were certain areas of the necropolis selected for burial in certain time periods; what were the tombs’ spatial relations to contemporaneous and older monuments; and what effect did earlier structures have on the positioning of tombs and structuring of the necropolis in later times? This study adopts landscape biography as a conceptual tool to study the long-time interaction between people and landscapes
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