Watching sitcoms together : a discursive analysis

Neuronal nicotinic acetylcholine receptors (nAChRs) are involved in a plethora of fundamental biological processes ranging from muscle contraction to the formation of memories. The studies described in this work focus on the transcriptional regulation of the CHRNB4 gene, which encodes the !4 subunit of neuronal nAChRs. We previously identified a regulatory sequence (5 – CCACCCCT –3 ), or “CA box”, critical for CHRNB4 promoter activity in vitro. Here I report transcription factor interaction at the CA box along with an in vivo analysis of CA box transcriptional activity. My data indicate that Sp1, Sp3, Sox10 and c-Jun interact with the CHRNB4 CA box in the context of native chromatin. Using an in vivo transgenic approach in mice, I demonstrated that a 2.3-kb fragment of the CHRNB4 promoter region, containing the CA box, is capable of directing cell-type specific expression of a reporter gene to many of the brain regions that endogenously express the CHRNB4 gene. Site-directed mutagenesis was used to test the hypothesis that the CA box is critical for CHRNB4 promoter activity in vivo. Transgenic animals were generated in which LacZ expression is driven by a mutant form of the CA box. Reporter gene expression was not detected in any tissue or cell type at ED18.5. Similarly, I observed dramatically reduced reporter gene expression at PD30 when compared to wild type transgenic animals, indicating that the CA box is an important regulatory feature of the CHRNB4 promoter. ChIP analysis of brain tissue from mutant transgenic animals demonstrated that CA box mutation results in decreased interaction of the transcription factor Sp1 with the CHRNB4 promoter.

Two-component systems are the most common mechanism of transmembrane signal transduction in bacteria and are involved in many cellular processes. They control the expression of genes for nutrient acquisition, virulence, antibiotic resistance, and numerous other processes in diverse bacteria. These systems are often used by soil bacteria that have to adapt to frequent changes in nutritional availability and in environmental conditions to regulate their gene expression. By contrast, bacteria that live in stable niches (symbionts of aphids, extremophiles or some marine hydrocarbon-degrading bacteria, etc.) seem to have less regulatory systems. Recently, a functionally active two- component system (named PhMAlRS) probably involved in the of expression regulation of a C4-dicarboxylate transporter system was identified in the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125. Our data demonstrated that the expression of the C4-dicarboxylate transporter system (consisting of genes coding for an outer membrane porin and a periplasmic transporter, renamed Phdct A and B, respectively) is induced by the presence of L-malate under the control of the PhMalRS two-component regulatory system. The DNA region located upstream the PhdctA porin gene was further investigated; two different transcriptional start sites and two different promoter sequences were defined, one of which is a typical σ core promoter. A 53 bp inverted repeat sequence located 77 bp upstream the distal transcriptional start site was also identified. Functional analysis of this element showed that the inverted repeat sequence was specifically recognised by protein extracts of PhTAC125 only when the cells were grown in the presence of L-malate, suggesting a putative regulatory role for this DNA region. We can speculate that this DNA sequence represents the cis-acting region requested for the binding of transcriptional regulatory proteins leading to the induction of the PhdctAB operon expression. These results demonstrated the occurrence of a fine transcriptional mechanism that regulates the expression of a C4-dicarboxylate transporter operon in Pseudoalteromonas haloplanktis TAC125. In the presence of L-malate, the PhMalRS regulatory system controls the expression of the PhdctA and B genes very likely through binding of a regulatory protein to the cis-acting region located upstream the outer membrane porin gene. The interaction of the regulatory protein with this DNA sequence probably strengthens the binding of RNA polymerase on the σ core promoter sequence and activates the transcription of downstream genes responsible for L-malate uptake.

Previously, competence was conceptualized as a static individual construct that could be measured with regard to grammatical, sociolinguistic, pragmatic, and discursive dimensions of second language (L2) knowledge. This perspective was criticized with the emergence of constructivist views in second language acquisition (SLA), and interaction was assumed to be coconstructed in specific contexts by all the members of the group, and was referred to as interactional competence. This study aimed at investigating the highlighted features of interactional competence from raters' point of view. The raters were also required to compare and contrast the differences between the performance of paired vs. group interactions. For this purpose, 16 male and female proficient English language and literature students of Shiraz university participated in the study; also, 10 experienced raters were chosen to rate the performances. The participants were given a set of controversial questions, once to argue their viewpoints in four-member groups, and once more in paired interaction. Having videotaped the discussions, the raters were asked to watch the clips and were interviewed to comment their perspective. The detailed analysis of the transcription of interviews revealed at least three aspects of interactional competence, each with some subcategories: management, engagement and attention, and paralinguistic aspects. Moreover, peer-to-peer interactions were filled with turn-taking, other-initiated self-repair, use of pauses and wait times, backchanneling, and facial features such as eye contact. Group performances were prominent with self-initiated self-repair, open-ended clarification requests, and employment of vocal features.

Members of the Runx family of transcription factors play essential roles in the differentiation and development of several organ systems. Here we address the contribution of the osteoblast-related Runx gene, Runx2 , to the osteogenic and chondrogenic differentiation of mesenchymal stem cells. Using a transgenic mouse model, we observe Runx2 transcription through one of its two known promoters (designated P1 in pre-cartilaginous mesenchymal condensations as early as E9.5. Runx2 gene activity is later repressed at the onset of cartilage formation, both in vivo and in vitro , necessitating examination of the regulation and function of Runx2 in mesenchymal stem cells. We demonstrate that Runx2 gene activity is repressed by the direct interaction of the homeodomain transcription factor Nkx3.2 with the proximal Runx2 P1 promoter. This repression was found to be required for the progression of BMP-induced chondrogenesis, thereby identifying Runx2 as a modulator of BMP activity in the chondrogenic as well as osteogenic differentiation program. To further understand the regulation of the Runx2 P1 promoter and to determine the contribution of P1-derived gene product, Runx2 Type II, to the formation of mineralized tissue, we have generated a Runx2 Type II- LacZ gene replacement mouse model in which the initial coding sequences and splice donor sites of the Type II isoform are replaced with the LacZ reporter gene. Activity of the endogenous P1 promoter can therefore be monitored by β-galactosidase production. Analysis of Runx2 Type II-LacZ mice demonstrates that the P1 promoter is transcriptionally most active in mature osteoblasts, but its product, Runx2 Type II is dispensable for embryonic skeletal formation. Lastly, we examine the link between growth control and osteogenic differentiation by tissue-specific deletion of the Mdm2 proto-oncogene in developing skeletal tissues of the mouse embryo. Loss of Mdm2 results in impaired bone formation, with skeletal elements exhibiting lower bone mineral content and higher porosity. Ex vivo cultures of calvarial osteoprogenitor cells exhibit severely decreased osteoblastogenesis and bone nodule formation accompanied by a failure to activate Runx2 gene activity. These findings suggest that Mdm2 is required for inhibition of p53 activity that ultimately allows for post-confluent proliferation and induction of Runx2 during maturation of the osteogenic phenotype. Taken together, our findings suggest that Runx2 modulates the commitment of progenitor cells to the osteogenic and chondrogenic lineages, and that Runx2 activity is inextricably linked to mechanisms that control cellular proliferation.

We describe some aspects of a Broadcast News recognition system based on hybrid HMM/MLP acoustic modeling. These include the use of novel ‘modulation spectrogram’ features which are combined with conventional models at the posterior probability level, some experiments with nonlinear segment normalization, and an investigation of the interaction of model size and training set size for an multilayer perceptron (MLP) acoustic classifier. We also report preliminary results of incorporating gender-dependence into this system. 1. Background In recent years, we and our colleagues have promoted the exploration of novel, poorly understood, but promising approaches to speech recognition [2]. While such deviations from incremental improvements might initially hurt performance, the subset of the new methods that would ultimately prove useful would not be found without such explorations. This past year, we attempted to follow this advice, while still developing a system with reasonable performance on the automatic transcription of Broadcast News speech. An additional goal was finding approaches that would work well in combination with components developed by our SPRACH partners at Cambridge and Sheffield. Finally, previous published results seemed to indicate that, while the hybrid HMM/connectionist approach was successful for moderate sized training corpora, it did not appear to take advantage of significant increases in the size of the corpus. Recently improved computational capabilities at ICSI permitted tests to determine if this was true. Given these considerations, we developed experimental Broadcast News systems that incorporated:

Fluorescence and Labelling: How to choose and what to do -- Fluorescent biosensors: design and application to motor proteins -- Rapid Reaction Kinetic Techniques -- Fluorescence to study the ATPase mechanism of Motor Proteins -- Use of pyrene labelled actin to probe actin myosin interactions; kinetic and equilibrium studies -- Fluorescent methods to study transcription initiation and transition into elongation -- Single-molecule and single-particle imaging of molecular motors in vitro and in vivo -- Fluorescence methods in the investigation of the DEAD-box helicase mechanism -- Use of Fluorescent Techniques to Study the In Vitro Movement of Myosins -- Fluorescence Tracking of Motor proteins in vitro -- Measuring Transport of Motor Cargos -- Measuring two at the same time: Combining Magnetic Tweezers with Single-Molecule FRET -- Using fluorescence to study actomyosin in yeasts.

Analysis of transcription factor DNA interactions utilising energy filtered transmission electron microscopy

Emerging evidence in both vertebrates and invertebrates is redefining glia as active and mobile players in synapse formation, maturation and function. However, the molecular mechanisms through which neurons and glia interact with each other to regulate these processes is not well known. My thesis work begins to understand how glia use secreted factors to modulate synaptic function. We use Drosophila melanogaster, a simple and genetically tractable model system, to understand the molecular mechanisms by which glia communicate with neurons at glutamatergic neuromuscular junctions (NMJs). We previously showed that a specific subtype of glia, subperineurial peripheral glia cells (SPGs), establish dynamic transient interactions with synaptic boutons of the NMJ and is required for synaptic growth. I identified a number of potential functional targets of the glial transcription factor, reverse polarity (repo) using ChIP-chip. I found that one novel target of Repo, Wg, is expressed in SPGs and is regulated by repo in vivo. Wnt/Wg signaling plays a pivotal role during synapse development and plasticity, including the coordinated development of the molecular architecture of the synapse. While previous studies demonstrated that Wg is secreted by motor neurons, herein I provide evidence that a significant amount of Wg at the NMJ is additionally provided by glia. I found that Wg derived from SPGs is required for proper GluR distribution and electrophysiological responses at the NMJ. In summary, my results show that Wg expression is

Although the concept of ‘face’ has recently been the focus of attention in language pragmatics, face theory and research have dealt with individual rather than social aspects of human interactions (Arundale, 2013). In order to assess the epistemological and methodological dimensions of face in recent literature, this qualitative meta-synthetic study examines the concept of face in intercultural and multicultural communicative interactions. A total of 13 intercultural face studies published in two leading journals, Journal of Pragmatics and Intercultural Pragmatics, were identified and a thorough qualitative content analysis was conducted to identify the core themes and commonalities. The emerging themes portrayed the concept of face as culture and language specific, relational, interactional, and location-specific, co-constructed and negotiated by the participants in the ongoing discourse activities. Concerning the methodology adopted by researchers in the realms of pragmatics in general and face studies in particular, it is noted that most of intercultural face studies employed mainly audio and video interaction recordings, observations, interviews, and field notes and procedures like including linguistic ethnography, conversation analysis, and interactional sociolinguistic procedures were not used while it seems a more comprehensive understanding of face is achieved through ethnographic, conversation analytic, and interactional sociolinguistic studies in a range of different communicative contexts. The study nominates some methodological aspects of face for further studies in the intercultural pragmatics research area.

Atom lithography is a technique to structure layers of atoms during deposition, using interactions of near-resonant light fields with neutral atoms. The basic scheme uses a standing wave light field, aligned just above a substrate, while a beam of atoms impinges perpendicularly on the standing wave light field. The interaction of the light field and the atoms focuses the atoms towards the crests or troughs of the standing wave intensity, dependent on the tuning of the light field. The focused atoms are subsequently deposited on the substrate, resulting in an array of lines, whose periodicity is determined by the wavelength of the light field. The standing wave light field can therefore be seen as an array of lenses, focusing the atom beam into an array of lines. The first experiments on atom lithography were performed in the 1990s with sodium and chromium. In this thesis experiments with iron are described, which is a magnetic element and thus allows for the creation of magnetic nanostructures. To focus atom beams into structures using atom lithography, well-colimated atom beams are required. The most common technique to create collimated atom beams is transverse laser cooling, but iron has no closed optical transition suitable for laser cooling. Fortunately Smeets and Te Sligte found that even then atom lithography of iron is possible. If the standing wave light field is considered to be an array of lenses, the focusing of the atom beam on a single lens is determined by the local collimation of the atom beam at that position. This local collimation is determined by the geometry of the beam source and the distance of the beam source to the standing wave lens. Using a small beam source (e.g. 1 mm diameter) positioned far from the standing wave (e.g. 1 m), the geometrically collimated atom beam is suitable for atom lithography. Chapter 3 shows what the implications of geometric collimation are on the structure formation in atom lithography. The geometric effects that locally collimate the atom beam on the sample also introduce local offset angles of the atom beam with respect to the focusing light field. Structure formation has been observed with lines of up to 7 nm high on a background layer of 15 nm average height, over areas of up to 400 µm × 6 mm. This indicates that the offset angles can vary over an 8 mrad range, which is more than an order of magnitude larger than the local angle of collimation. The offset angle influence the local geometry of the deposited structures: an increasing offset angle decreases the local line height, increases the width and creates a skewness in the local line shape. The local geometry of the lines has been modelled with a Monte Carlo particle tracking model and the results were compared to experiments. It was found that the highest and narrowest lines suffer from significant broadening due to surface diffusion in experiments, limiting the achievable structure width of iron on SiOx samples to about 80 nm. We have also found that in atom lithography without laser cooling, each standing wave lens is effectively imaging the source geometry onto the substrate. We therefore propose using structured atom beam sources to image more complex patterns on sub-wavelength scales in a parallel way. The reason to use iron in atom lithography, is the option to create magnetic nanostructures. However, in previous experiments no clear magnetic signature of the atom lithographic structuring of iron was found. Therefore in Chapter 4 firstly the magnetic properties of unstructured layers of iron (Fe), nickel (Ni) and FexNi1-x are investigated. These layers are all ferromagnetic, but with a reduced magnetic moment compared to bulk values due to contaminations and crystal growth effects. As a reference for periodic atom lithography structures, periodic line structures are created with interference lithography in a polymer layer and onto these structures thin layers of FexNi1-x are shadow deposited, thereby creating a layer periodically modulated in both height and elemental composition. This periodic modulation in composition has been observed with SEM-EDX on sub-micron scales. The structures showed a clear magnetic anisotropy with an easy axis along the direction of the lines, in accordance with expectations. In Chapter 5, the magnetic properties of atom lithographic iron line structures are presented. Using MOKE microscopy, direct comparison of structured and unstructured parts of a sample is possible, which allows for the observation of clear magnetic signatures due to the atom lithographic structuring. In layers of an average thickness of about 15 nm, no anisotropy is induced by the line structures, while a magnetic easy axis along the direction of the lines is expected. The line structures introduce an isotropic increase in the coercivity of the layers, indicating that the line structures can be considered as isotropic corrugations instead of directional line structures. For layers of 30 nm average thickness and thus higher line structures, a clear magnetic anisotropy is observed for the highest line structures. This anisotropy can be seen as a magnetic easy axis along the direction of the lines, as expected for line structures. However, we also observe a sharp increase in coercivity for applied fields perpendicular to the lines. This phenomenon is intriguing and may be explained by a pinning of head-to-head domain walls along the direction of the lines. In Chapter 5, we also report on the first results of co-deposition of FexNi1-x, where the Fe is structured into lines using atom lithography, while the Ni is deposited uniformly, thereby creating an alloy of modulating composition. Magnetic analysis of these structures indicates that these structures are anisotropic, both the coercivity and the shape of domain walls is dependent on the angle of the applied field relative to the line structures. Finally in Chapter 6, we investigate the possibilities to focus a thermal beam of atoms into a single 100 nm spot using light fields, thereby creating a nanopencil suitable for deposition of nanostructures. A Monte Carlo particle tracking program was developed to model the all optical focusing or funneling of 10 µm sized atom beams to a 100 nm spot. This model included effects of initial beam divergence, magnetic substructure, laser cooling, and spontaneous as well as stimulated diffusion and it was applied to a number of promising light field configurations. The best results obtained for experimentally realistic settings are a beam focused to a full width at half maximum of FWHM = 0.55 µm in a blue detuned hollow beam where atoms are focused towards the dark center, or a FWHM = 0.31 µm in a red detuned axicon light field, where atoms are focused towards the maximum intensity at the heart line. However, in the latter case the focused beam has a flux only 25 times larger than the background flux, which is unpractical for applications. The limiting factors of all schemes are heating due to stimulated diffusion and the limited interaction time available for a thermal beam of atoms. A nanopencil could be possible if it were based on the focussing of a slow and / or monochromatic atom beam, but this would seriously complicate the practical application of such a device.

Examining Play Among Young Children in Single-age and Multi-age Preschool Classroom Settings by Mia Song Youhne Dr. Nancy Sileo, Examination Committee Chair Associate Professor of Special Education University of Nevada, Las Vegas Advocates for multi-age classrooms claim multi-age groupings benefit children (Brynes, Shuster, & Jones, 1994). Currently, there is a lack of research examining play among students in multi-age classrooms. If indeed there is a positive benefit of play among children, research is needed to examine these behaviors among and between young children in single-age and multi-age classrooms. The purpose of this study was to determine if young children benefit from increased play opportunities. This qualitative study utilized observations, interviews, and questionnaires to gather data from teachers, parents, and children regarding play interactions in both single-age and multi-age classrooms. The intent of this study was to provide a rationale for why multi-age programs should be developed or continued. Participants in this study included teachers and parents who completed questionnaires and children who participated in video taped observations and interviews. This study took place in a fully inclusive early childhood center. Observations of the play engagements of children were video taped in both the indoor and outdoor sandbox settings. During the five weeks of video taping, 281 play segments were recorded resulting in 1549 occurrences of play. Based on the play observations, it appeared that young children in multi-age classrooms engaged in more than one type of play more frequently than young children in single-age classrooms. Further, young children in multi-age classrooms initiated play more frequently. However, typically developing young children in multi-age classrooms did not initiate play with young children with disabilities more frequently than typically developing young children in single-age classrooms. The interviews with children indicated that young children were aware of their own play interactions. Based on the data collected from the questionnaires of teachers and parents, it appeared these two groups had similar views of the value of play and believed it to be developmentally appropriate and a critical learning process. Professionals in the field of early childhood education should consider the results of this study when designing, developing, and implementing single and multi-age programs for young children with and without disabilities. Moreover, professionals should consider the impact of play on the development of young children when designing curricula.

This thesis focuses on how a group of linguistically and culturally diverse individuals in an employment preparation class for immigrants to Canada use communicative strategies and resources to build common ground, that is, how they use language to form a socially cohesive group that foregrounds shared knowledge, shared relational identity, in-group membership and shared attitudes and feelings. The thesis draws from a 12-week ethnographically informed study using participant observation with audio recording and semi-structured interviews as the main methods of data collection. It builds on the combined insights drawn from the well established discipline of interethnic communication and the relatively new but growing field of research on English as a lingua franca. While the former illuminates factors that make intercultural communication problematic, the latter sheds light on what makes it work despite cultural differences and linguistic limitations. In analysing the data, which consists primarily of transcriptions from audio recordings of spoken classroom interactions, the thesis draws analytic inspiration from scholarship situated in discourse analysis, interactional sociolinguistics and applied linguistics. It borrows concepts from the Communities of Practice framework to understand how individuals from highly diverse backgrounds develop shared ways of talking/behaving and negotiate interactional norms. The thesis contributes to academic knowledge in several ways. It challenges common assumptions about iscommunication in intercultural contexts. It shows miscommunication episodes as potentially productive sites for negotiating meaning and restructuring social relations. It argues that the notion of ‘national’ culture, which has fallen into disfavour amongst scholars, should not simply be dismissed because ananalysis of the data collected suggests that it can serve as a multifaceted interactional resource for speakers alongside other identity categories. An important contribution of this thesis to the field of intercultural communication lies in its careful attention to what participants actually do in interaction over an extended period of time rather than starting from any a priori assumptions.

BRIEF SESSION DESCRIPTION: Conscious attention to reading improves all students’ comprehension of complex content and provides a strong basis for effective writing. Strategies developed at INTO Mason can be used to prepare students for more advanced summary and synthesis writing and to teach students to write for different audiences by developing genre awareness and critical thinking skills and by teaching them to use common rhetorical elements in their own writing. These strategies can be used across a range of disciplines. After attending the session, participants will be able to identify common rhetorical elements in written texts and to use rhetorical elements to structure reading and writing assignments in order to help students improve their understanding of course content and expectations and become more effective writers. **Participants should bring an assignment (on paper) they want to revise/change and a reading (PDF) that can be connected to the assignment (as a source or a sample). _______________________________________________________________ FULL ABSTRACT: Research on multilingual learners has found that receptive skills (reading and listening) are the foundation of successful production (writing and speaking) (Haan and Mallett 2016). Conscious attention to reading improves all students’ comprehension of complex content and provides a strong basis for effective writing. In this workshop, participants will practice identifying common rhetorical elements in written texts, analyzing those elements, and using those elements to begin shaping a writing project for undergraduate or graduate students in any discipline. Participants should bring an assignment (on paper) they want to revise/change and a reading (PDF) that can be connected to the assignment (as a source or a sample). After attending the session, participants will have identified at least one research-supported strategy (small change) that they can incorporate in their teaching to address a challenge or need in their course. Participants will also be aware of resources (books, websites, video series) to help them continue the process of identifying and implementing small changes. Finally, they will be connected to colleagues who are also interested in making small changes and can provide support and accountability moving forward. (We'd be thrilled if new teaching development groups emerged from the session.) **Participants should bring an assignment (on paper) they want to revise/change and a reading (PDF) that can be connected to the assignment (as a source or a sample).A‚ _______________________________________________________________ FULL ABSTRACT: Research on multilingual learners has found that receptive skills (reading and listening) are the foundation of successful production (writing and speaking) (Haan and Mallett 2016). Conscious attention to reading improves all studentsA¢â‚¬â„¢ comprehension of complex content and provides a strong basis for effective writing. In this workshop, participants will practice identifying common rhetorical elements in written texts, analyzing those elements, and using those elements to begin shaping a writing project for undergraduate or graduate students in any discipline. Participants should bring an assignment (on paper) they want to revise/change and a reading (PDF) that can be connected to the assignment (as a source or a sample). After attending the session, participants will have identified at least one research-supported strategy (small change) that they can incorporate in their teaching to address a challenge or need in their course. Participants will also be aware of resources (books, websites, video series) to help them continue the process of identifying and implementing small changes. Finally, they will be connected to colleagues who are also interested in making small changes and can provide support and accountability moving forward. (We'd be thrilled if new teaching development groups emerged from the session.)

This research investigates the ‘performativity’ of the ‘author function’ through collaging the audio recordings of American poet Sylvia Plath. The ‘author function’ is a term by Michel Foucault to describe how readers attribute certain characteristics that they believe belong to the author and ascribe them to the writing. ‘Performativity’ is a term used by Judith Butler to describe a set of actions that ascribe and predetermine a set of attributes to a subject through his or her gender, age, timeframe, nationality and race. The ‘performativity’ of the ‘author function’ appropriates these characteristics and attributes them to the author. How the determination of an authorial identity translates to the interaction of the practice component of the project, which includes several components of digital collage, is through attributions that readers make in the creation of an author. The practice component of the project consists of the collage of audio and video recordings, the programming of video with Max/MSP/Jitter, ‘performative’ elements and collage poetry on Twitter. The audio component was collaged from two poems entitled ‘Lady Lazarus’ and ‘The Applicant’ that Plath read to the British Council in 1962 to form a new poem entitled Lady/Applicant: The Lazarus. The video component consists of collaging recorded video clips of storefront and street signs in Camden, London, where she is associated with living and committing suicide at. A second video collage entitled Shadows/Shadows/Tomb takes place at a cemetery close to my residence in 2011 and documents symbols of death that reference my own authorial identity. The second set of videos run on a Max/MSP/Jitter patch that display four screens of filmed texts inscribed on tombstones that play four streaming poems through a systematic structure of boxes. The screens are displayed in each box and sourced from separate folders to display and play the film clips. The practice of collage and constraint-based poetry complicates the constitution of being the author when the collagist of Plath’s poetry is a different gender than hers. This research then expands on how identity radically shifts in the text when the subject and the collagist have very different identities. The radical shift in a collage takes place within a predefined and generalized concept of the reader as determined by Stanley Fish, a prominent writer on the subject of ‘reader-response criticism’, who believes that one way a reader could be approached is through his or her relationship with the writing.

Visual information, in the form of images and video, comes from the interaction of light with objects. Illumination is a fundamental element of visual information. Detecting and interpreting illumination effects is part of our everyday life visual experience. Shading for instance allows us to perceive the three-dimensional nature of objects. Shadows are particularly salient cues for inferring depth information. However, we do not make any conscious or unconscious effort to avoid them as if they were an obstacle when we walk around. Moreover, when humans are asked to describe a picture, they generally omit the presence of illumination effects, such as shadows, shading, and highlights, to give a list of objects and their relative position in the scene. Processing visual information in a way that is close to what the human visual system does, thus being aware of illumination effects, represents a challenging task for computer vision systems. Illumination phenomena interfere in fact with fundamental tasks in image analysis and interpretation applications, such as object extraction and description. On the other hand, illumination conditions are an important element to be considered when creating new and richer visual content that combines objects from different sources, both natural and synthetic. When taken into account, illumination effects can play an important role in achieving realism. Among illumination effects, shadows are often integral part of natural scenes and one of the elements contributing to naturalness of synthetic scenes. In this thesis, the problem of extracting shadows from digital images is discussed. A new analysis method for the segmentation of cast shadows in still and moving images without the need of human supervision is proposed. The problem of separating moving cast shadows from moving objects in image sequences is particularly relevant for an always wider range of applications, ranging from video analysis to video coding, and from video manipulation to interactive environments. Therefore, particular attention has been dedicated to the segmentation of shadows in video. The validity of the proposed approach is however also demonstrated through its application to the detection of cast shadows in still color images. Shadows are a difficult phenomenon to model. Their appearance changes with changes in the appearance of the surface they are cast upon. It is therefore important to exploit multiple constraints derived from the analysis of the spectral, geometric and temporal properties of shadows to develop effective techniques for their extraction. The proposed method combines an analysis of color information and of photometric invariant features to a spatio-temporal verification process. With regards to the use of color information for shadow analysis, a complete picture of the existing solutions is provided, which points out the fundamental assumptions, the adopted color models and the link with research problems such as computational color constancy and color invariance. The proposed spatial verification does not make any assumption about scene geometry nor about object shape. The temporal analysis is based on a novel shadow tracking technique. On the basis of the tracking results, a temporal reliability estimation of shadows is proposed which allows to discard shadows which do not present time coherence. The proposed approach is general and can be applied to a wide class of applications and input data. The proposed cast shadow segmentation method has been evaluated on a number of different video data representing indoor and outdoor real-world environments. The obtained results have confirmed the validity of the approach, in particular its ability to deal with different types of content and its robustness to different physically important independent variables, and have demonstrated the improvement with respect to the state of the art. Examples of application of the proposed shadow segmentation tool to the enhancement of video object segmentation, tracking and description operations, and to video composition, have demonstrated the advantages of a shadow-aware video processing.