Weaving a pattern from disparate threads: lamin function in nuclear assembly and DNA replication

The major residual structure that remains associated with the nuclear envelope following extraction of isolated nuclei or oocyte germinal vesicles with non-ionic detergents, nucleases and high salt is the lamina (Fawcett, 1966; Aaronson and Blobel, 1975; Dwyer and Blobel, 1976). The nuclear lamina is composed of intermediate filament proteins, termed lamins (Gerace and Blobel, 1980; Shelton et al., 1980), which polymerise to form a basket-weave lattice of fibrils, which covers the entire inner surface of the nuclear envelope and interlinks nuclear pores (Aebi et al., 1986; Stewart and Whytock, 1988; Goldberg and Allen, 1992). At mitosis, the nuclear envelope and the lamina both break down to allow chromosome segregation. As a consequence, each structure has to be rebuilt during anaphase and telophase, allowing cells an opportunity to reposition chromosomes (Heslop-Harrison and Bennett, 1990) and to reorganise looped chromatin domains (Franke, 1974; Franke et al., 1981; Hochstrasser et al., 1986), which may in turn control the use of subsets of genes. Because of the position that it occupies, its dynamics during mitosis and the fact that it is an essential component of proliferating cells, the lamina has been assigned a number of putative roles both in nuclear metabolism and in nuclear envelope assembly (Burke and Gerace, 1986; Nigg, 1989). However, to date there is little clear cut evidence that satisfactorily explains the function of the lamina in relation to its structure. In this Commentary we will describe some of the recent work that addresses this problem and attempt to provide a unified model for the role of lamins in nuclear envelope assembly and for the lamina in the initiation of DNA replication

Watching movies on netflix: Investigating the effect of screen size on viewer immersion

Film and television content is moving out of the living room and onto mobile devices - viewers are now watching when and where it suits them, on devices of differing sizes. This freedom is convenient, but could lead to differing experiences across devices. Larger screens are often believed to be favourable, e.g. to watch films or sporting events. This is partially supported in the literature, which shows that larger screens lead to greater presence and more intense physiological responses. However, a more broadly-defined measure of experience, such as that of immersion from computer games research, has not been studied. In this study, 19 participants watched content on three different screens and reported their immersion level via questionnaire. Results showed that the 4.5-inch phone screen elicited lower immersion scores when compared to the 13-inch laptop and 30-inch monitor, but there was no difference when comparing the two larger screens. This suggests that very small screens lead to reduced immersion, but after a certain size the effect is less pronounced

Time domain reconstruction of sound speed and attenuation in ultrasound computed tomography using full wave inversion

Ultrasound computed tomography (USCT) is a non-invasive imaging technique that provides information about the acoustic properties of soft tissues in the body, such as the speed of sound (SS) and acoustic attenuation (AA). Knowledge of these properties can improve the discrimination between benign and malignant masses, especially in breast cancer studies. Full wave inversion (FWI) methods for image reconstruction in USCT provide the best image quality compared to more approximate methods. Using FWI, the SS is usually recovered in the time domain, and the AA is usually recovered in the frequency domain. Nevertheless, as both properties can be obtained from the same data, it is desirable to have a common framework to reconstruct both distributions. In this work, an algorithm is proposed to reconstruct both the SS and AA distributions using a time domain FWI methodology based on the fractional Laplacian wave equation, an adjoint field formulation, and a gradient-descent method. The optimization code employs a Compute Unified Device Architecture version of the software k-Wave, which provides high computational efficiency. The performance of the method was evaluated using simulated noisy data from numerical breast phantoms. Errors were less than 0.5% in the recovered SS and 10% in the AA. V

A semi-Markov model for stroke with piecewise-constant hazards in the presence of left, right and interval censoring.

This paper presents a parametric method of fitting semi-Markov models with piecewise-constant hazards in the presence of left, right and interval censoring. We investigate transition intensities in a three-state illness-death model with no recovery. We relax the Markov assumption by adjusting the intensity for the transition from state 2 (illness) to state 3 (death) for the time spent in state 2 through a time-varying covariate. This involves the exact time of the transition from state 1 (healthy) to state 2. When the data are subject to left or interval censoring, this time is unknown. In the estimation of the likelihood, we take into account interval censoring by integrating out all possible times for the transition from state 1 to state 2. For left censoring, we use an Expectation-Maximisation inspired algorithm. A simulation study reflects the performance of the method. The proposed combination of statistical procedures provides great flexibility. We illustrate the method in an application by using data on stroke onset for the older population from the UK Medical Research Council Cognitive Function and Ageing Study

Fixed Effect Estimation of Large T Panel Data Models

This article reviews recent advances in fixed effect estimation of panel data models for long panels, where the number of time periods is relatively large. We focus on semiparametric models with unobserved individual and time effects, where the distribution of the outcome variable conditional on covariates and unobserved effects is specified parametrically, while the distribution of the unobserved effects is left unrestricted. Compared to existing reviews on long panels (Arellano and Hahn 2007; a section in Arellano and Bonhomme 2011) we discuss models with both individual and time effects, split-panel Jackknife bias corrections, unbalanced panels, distribution and quantile effects, and other extensions. Understanding and correcting the incidental parameter bias caused by the estimation of many fixed effects is our main focus, and the unifying theme is that the order of this bias is given by the simple formula p/n for all models discussed, with p the number of estimated parameters and n the total sample size.Comment: 40 pages, 1 tabl

Old Habits Die Hard: A Diary Study of On-Demand Video Viewing

On-demand video services allow viewers to access media wherever and whenever they like, on a wide variety of devices. These services have become extremely popular in recent years, but exactly how people interact with these services has not been studied in detail. We conducted a diary study with nine households to investigate this, and present the preliminary results in this paper. Participants took advantage of the freedom and choice these services provided, watching on different devices, in different locations, and for extended periods of time. However, the majority of viewing conformed to traditional patterns, occurring in the evening on large screens, though viewing on a laptop was slightly more popular than the television. We found that usage of on-demand services was influenced by situational factors such as location and the devices that are available

Film, interrupted: Investigating how mobile device notifications affect immersion during movies

Mobile devices are increasingly used while watching video, both as a secondary device and for dedicated viewing. However, devices frequently issue notifications that can interrupt viewing. This study investigated the effect of interruptions from notifications on viewer immersion. Participants watched 10 minutes of a movie without notifications, and 10 minutes while receiving message notifications. There were two participant groups: one watched video on a 30-inch monitor with messages sent to a separate smartphone; while another watched on a smartphone while also receiving messages on it. Viewer immersion was assessed after each condition via questionnaire. We also considered message response times. Results showed that immersion scores were lower when the video was interrupted with notifications, regardless of viewing device. Message response times were fastest when using the phone as a secondary device. Our results suggest that device-driven interruptions should be minimised for an immersive film experience

Development of a questionnaire to measure immersion in video media: The Film IEQ

Researchers and practitioners are keen to understand how new video viewing practices driven by technological developments impact viewers' experiences. We detail the development of the Immersive Experience Questionnaire for Film and TV (Film IEQ). An exploratory factor analysis based on responses from 414 participants revealed a four-factor structure of (1) captivation, (2) real-world dissociation, (3) comprehension, and (4) transportation. We validated the Film IEQ in an experiment that replicated prior research into the effect of viewing on screens of varying size. Responses captured by the Film IEQ indicate that watching on a small phone screen reduces the viewer's level of comprehension, and that this negatively impacts the viewing experience, compared to watching on a larger screen. The Film IEQ allows researchers and practitioners to assess video viewing experiences using a questionnaire that is easy to administer, and that has been empirically validated