Fast MLE Computation for the Dirichlet Multinomial

Given a collection of categorical data, we want to find the parameters of a Dirichlet distribution which maximizes the likelihood of that data. Newton's method is typically used for this purpose but current implementations require reading through the entire dataset on each iteration. In this paper, we propose a modification which requires only a single pass through the dataset and substantially decreases running time. Furthermore we analyze both theoretically and empirically the performance of the proposed algorithm, and provide an open source implementation

An advanced telerobotic system for shuttle payload changeout room processing applications

To potentially alleviate the inherent difficulties in the ground processing of the Space Shuttle and its associated payloads, a teleoperated, semi-autonomous robotic processing system for the Payload Changeout Room (PCR) is now in the conceptual stages. The complete PCR robotic system as currently conceived is described and critical design issues and the required technologies are discussed

A model for fluvial bedrock incision by impacting suspended and bed load sediment

A mechanistic model is derived for the rate of fluvial erosion into bedrock by abrasion from uniform size particles that impact the bed during transport in both bed and suspended load. The erosion rate is equated to the product of the impact rate, the mass loss per particle impact, and a bed coverage term. Unlike previous models that consider only bed load, the impact rate is not assumed to tend to zero as the shear velocity approaches the threshold for suspension. Instead, a given sediment supply is distributed between the bed and suspended load by using formulas for the bed load layer height, bed load velocity, logarithmic fluid velocity profile, and Rouse sediment concentration profile. It is proposed that the impact rate scales linearly with the product of the near-bed sediment concentration and the impact velocity and that particles impact the bed because of gravitational settling and advection by turbulent eddies. Results suggest, unlike models that consider only bed load, that the erosion rate increases with increasing transport stage (for a given relative sediment supply), even for transport stages that exceed the onset of suspension. In addition, erosion can occur if the supply of sediment exceeds the bed load transport capacity because a portion of the sediment load is transported in suspension. These results have implications for predicting erosion rates and channel morphology, especially in rivers with fine sediment, steep channel-bed slopes, and large flood events

The Pornographic Digital Divide: Libraries and Forbidden Knowledge

Introduction: This paper does not present solutions to the use of pornography in public spaces such as the library nor does it reflect the opinions of the institution that pays my salary. Instead, it presents a dilemma and problematizes the use of and access to pornography and other taboo information materials by library users. Background: Pornography is the graphic representation of sexual acts. While hard copy formats certainly still exist, pornography is increasingly digital, moving from print to film to videocassette to the internet and DVD. Each of these digital formats requires the use of special equipment (VCR, computer with internet access, DVD player) that has its own associated purchase or rental costs. Information users without their own machines must either do without the information available only in these formats or seek out publicly available technology, such as that provided in the library. Dilemma: Librarians are the defenders of free speech and free access to information. We audibly hiss at the mention of CIPA, internet filters, and banned and challenged books. We follow a populist model of providing our user communities with the titles they want—even if we personally find romance novels trashy and the Captain Underpants series repugnant. So why do we treat porn as a special case? One of the most common statements librarians make about pornography begins: I don\u27t care what people do at home, but in a public place\u2026\u27 Does this mean that people without homes or private places do not have the right to access sexually explicit materials? Is sexual self-expression reserved for the upper/middle class who can afford privacy? If not, who provides the access, if not the library? If so, is there a line of what constitutes acceptable? Where is it drawn? Does the reason someone is looking at the information matter (e.g. Is looking at a penis for medical information somehow a \u27better\u27 use of the information than looking at it for sexual satisfaction?), and are we supposed to police the ways in which information is used/perceived, such as whether people get sexual satisfaction from a particular piece of information/image? If librarianship claims to be about providing people with the information they need without passing judgment, no matter what it happens to be for, can our anti-porn stance coexist with our ardent disapproval of censorship?\u2

Human Animal Chimeras For Therapeutic Protocols

Research on humans is limited, therefore human animal chimeras have been used to study human systems. A Human animal chimera is an animal containing animal and human cell lines. The primary goal of human animal chimera research is to establish an animal with human cellular characters, which can and should more realistically be able to imitate as closely as possible the in vivo situations in humans. This research is very important, because it allows scientists to study human systems in vivo using a humanized animal model. However ethical issues arise when experimenting with humans and animals being mixed together. Using information found on Touro College’s database, this article reviews studies done using human animal chimeras, and their potential benefits for therapeutic protocols