Engagement and retention of participants in a physical activity website

Background. Websites have the potential to deliver enhanced versions of targeted and tailored physical activity programs to large numbers of participants. We describe participant engagement and retention with a stage-based physical activity website in a workplace setting. Methods. We analyzed data from participants in the website condition of a randomized trial designed to test the efficacy of a print- vs. website-delivered intervention. They received four stage-targeted e-mails over 8 weeks, with hyperlinks to the website. Both objective and self-reported website use data were collected and analyzed. Results. Overall, 327 were randomized to the website condition and 250 (76%) completed the follow-up survey. Forty-six percent (n = 152) visited the website over the trial period. A total of 4,114 hits to the website were recorded. Participants who entered the site spent on average 9 min per visit and viewed 18 pages. Website use declined over time; 77% of all visits followed the first e-mail. Conclusions. Limited website engagement, despite the perceived usefulness of the materials, demonstrates possible constraints on the use of e-mails and websites in delivering health behavior change programs. In the often-cluttered information environment of workplaces, issues of engagement and retention in website-delivered programs require attention. (C) 2004 The Institute For Cancer Prevention and Elsevier Inc. All rights reserved.

Blocking the path from vagueness to four dimensionalism

There is a general form of an argument which I call the 'argument from vagueness' which attempts to show that objects persist by perduring, via the claim that vagueness is never ontological in nature and thus that composition is unrestricted. I argue that even if we grant that vagueness is always the result of semantic indeterminacy rather than ontological vagueness, and thus also grant that composition is unrestricted, it does not follow that objects persist by perduring. Unrestricted mereological composition lacks the power to ensure that there exist instantaneous objects that wholly overlap persisting objects at times, and thus lacks the power to ensure that there exists anything that could be called a temporal part. Even if we grant that such instantaneous objects exist, however, I argue that it does not follow that objects perdure. To show this I briefly outline a coherent version of three dimensionalism that grants just such an assumption. Thus considerations pertaining to the nature of vagueness need not lead us inevitably to accept perdurantism.

Epitope-blocking enzyme-linked immunosorbent assay for detection of antibodies to Ross River virus in vertebrate sera

We describe the development of an epitope-blocking enzyme-linked immunosorbent assay (ELISA) for the sensitive and rapid detection of antibodies to Ross River virus (RRV) in human sera and known vertebrate host species. This ELISA provides an alternative method for the serodiagnosis of RRV infections.

Website physical activity interventions: preferences of potential users

Information and communication technologies (particularly websites and e-mail) have the potential to deliver health behavior change programs to large numbers of adults at low cost. Controlled trials using these new media to promote physical activity have produced mixed results. User-centered development methods can assist in understanding the preferences of potential participants for website functions and content, and may lead to more effective programs. Eight focus group discussions were conducted with 40 adults after they had accessed a previously trialed physical activity website. The discussions were audio taped, transcribed and interpreted using a themed analysis method. Four key themes emerged: structure, interactivity, environmental context and content. Preferences were expressed for websites that include simple interactive features, together with information on local community activity opportunities. Particular suggestions included online community notice boards, personalized progress charts, e-mail access to expert advice and access to information on specific local physical activity facilities and services. Website physical activity interventions could usefully include personally relevant interactive and environmentally focused features and services identified through a user-centered development process.

theta-defensins prevent HIV-1 Env-mediated fusion by binding gp41 and blocking 6-helix bundle formation

Retrocyclin-1, a 0-defensin, protects target cells from human immunodeficiency virus, type 1 (HIV-1) by preventing viral entry. To delineate its mechanism, we conducted fusion assays between susceptible target cells and effector cells that expressed HIV-1 Env. Retrocyclin-1 (4 mu M) completely blocked fusion mediated by HIV-1 Envs that used CXCR4 or CCR5 but had little effect on cell fusion mediated by HIV-2 and simian immunodeficiency virus Envs. Retrocyclin-1 inhibited HIV-1 Env-mediated fusion without impairing the lateral mobility of CD4, and it inhibited the fusion of CD4-deficient cells with cells bearing CD4-independent HIV-1 Env. Thus, it could act without cross-linking membrane proteins or inhibiting gp120-CD4 interactions. Retrocyclin-1 acted late in the HIV-1 Env fusion cascade but prior to 6-helix bundle formation. Surface plasmon resonance experiments revealed that retrocyclin bound the ectodomain of gp41 with high affinity in a glycan-independent manner and that it bound selectively to the gp41 C-terminal heptad repeat. Native-PAGE, enzyme-linked immunosorbent assay, and CD spectroscopic analyses all revealed that retrocyclin-1 prevented 6-helix bundle formation. This mode of action, although novel for an innate effector molecule, resembles the mechanism of peptidic entry inhibitors based on portions of the gp41 sequence.

Investigations into the effect of LOS signal blocking on capacity of an indoor MIMO system

In indoor environments the properties of communication channel are affected by the presence of various objects which block the Line Of Sight signal propagation. For example, this occurs because of presence of movement of humans and furniture. In this paper, the effect of reflection and scattering due to the presence of such objects is studied with respect to the capacity of a multiple input multiple output (MIMO) wireless system. The carried out investigations are performed by applying a simple electromagnetic model, in which transmitting and receiving antennas of MIMO system, as well as signal blocking objects, are represented by wire dipoles. In order to provide a fair assessment, calculations of MIMO capacity are performed under both fixed transmitted power and fixed received power conditions.

Formalising progress properties of non-blocking programs

A non-blocking program is one that uses non-blocking primitives, such as load-linked/store-conditional and compare-and-swap, for synchronisation instead of locks so that no process is ever blocked. According to their progress properties, non-blocking programs may be classified as wait-free, lock-free or obstruction-free. However, a precise description of these properties does not exist and it is not unusual to find a definition that is ambiguous or even incorrect. We present a formal definition of the progress properties so that any confusion is removed. The formalisation also allows one to prove the widely believed presumption that wait-freedom is a special case of lock-freedom, which in turn is a special case of obstruction-freedom.

Implicit learning is not subject to blocking

Explicit (aware) learning has been shown to evidence certain characteristics, such as extinction, blocking, occasion setting, and reliance on context. These characteristics have not been assessed in implicit (unaware) learning. The current study investigated whether implicit learning is subject to blocking. Participants completed a cued reaction time task, where they watched rapid presentations of a random sequence of 8 pairs of shapes, and responded to two target shapes. One target was always preceded by a cue. The experimental group completed a pretraining phase where half the cue, one shape, was followed by the target. Both experimental and control groups completed a training phase where both elements of the cue, two shapes, were followed by the target. Both aware and unaware participants evidenced learning, whereby responding was faster for cued than uncued targets. Aware participants in the experimental group responded faster to targets preceded by the pretrained element than by the other element of the cue. Control and unaware experimental participants were faster to respond to targets preceded by either element of the cue. As blocking was only evident in aware participants, but implicit learning was observed in all participants, it is concluded that implicit learning is not subject to blocking.