A new and flexible method for constructing designs for computer experiments

We develop a new method for constructing "good" designs for computer experiments. The method derives its power from its basic structure that builds large designs using small designs. We specialize the method for the construction of orthogonal Latin hypercubes and obtain many results along the way. In terms of run sizes, the existence problem of orthogonal Latin hypercubes is completely solved. We also present an explicit result showing how large orthogonal Latin hypercubes can be constructed using small orthogonal Latin hypercubes. Another appealing feature of our method is that it can easily be adapted to construct other designs; we examine how to make use of the method to construct nearly orthogonal and cascading Latin hypercubes.Comment: Published in at http://dx.doi.org/10.1214/09-AOS757 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Praxis with Self-Advocates: Exploring Participatory Video as Radical Incrementalism

In this article, the authors report selected findings from a larger study where self-advocates from the disability rights movement created a series of short videos as part of a participatory research project. Self-advocates subsequently integrated these videos into a greater community organizing initiative. While the research process of this study has been published elsewhere, this piece will explore the idea of bridging participatory video, a collaborative research methodology, with community-based advocacy initiatives. The authors contend that this presents an opportunity for radical incrementalism in which to create a praxis driven predominantly by the voices on the margins versus the academic elite. In this article, a link to one of the videos is also included alongside participant reflections on the research process

Non-invasive monitoring of renal transplant recipients: Urinary excretion of soluble adhesion molecules and of the complement-split product C4d

Background: The number of inducible adhesion molecules known to be involved in cell-mediated allograft rejection is still increasing. In addition, recent data describe complement activation during acute humoral allograft rejection. The aim of this study was to assess whether specific molecules from either pathway are excreted into urine and whether they can provide useful diagnostic tools for the monitoring of renal transplant recipients. Methods: Urinary concentrations of soluble adhesion molecules (sICAM-1, sVCAM-1) and of the complement degradation product C4d were determined by standardized ELISA technique in 75 recipients of renal allografts and 29 healthy controls. Patient samples were assigned to four categories according to clinical criteria: group 1: acute steroid-sensitive rejection (ASSR, n=14), group 2: acute steroid-resistant rejection (ASRR, n=12), group 3: chronic allograft dysfunction (CAD, n=20) and group 4: stable graft function (SGF, n=29). Results: All patients with rejection episodes (groups 1-3) had significantly higher values of urinary sC4d compared with healthy controls and patients with stable graft function (p<0.05). The urinary levels of sVCAM-1 were significantly higher in group 2 (ASRR) compared with all other groups (p<0.001). Uniformly low amounts of s-VCAM-1 and complement-split product C4d were excreted by healthy controls (group 0). In contrast, urinary sICAM-1 concentration in healthy controls was almost as high as in group 2 (ASRR) whereas patients with a stable functioning graft (group 4) excreted significantly less sICAM-1 (p<0.05). Conclusion: The evaluation of sVCAM-1 and sC4d excretion in urine can provide a valuable tool with regard to the severity and type of allograft rejection. With respect to long-term allograft survival, serial measurements of these markers should have the potential to detect rejection episodes and prompt immediate treatment. Copyright (C) 2003 S. Karger AG, Basel

A terrestrial search for dark contents of the vacuum, such as dark energy, using atom interferometry

We describe the theory and first experimental work on our concept for searching on earth for the presence of dark content of the vacuum (DCV) using atom interferometry. Specifically, we have in mind any DCV that has not yet been detected on a laboratory scale, but might manifest itself as dark energy on the cosmological scale. The experimental method uses two atom interferometers to cancel the effect of earth's gravity and diverse noise sources. It depends upon two assumptions: first, that the DCV possesses some space inhomogeneity in density, and second that it exerts a sufficiently strong non-gravitational force on matter. The motion of the apparatus through the DCV should then lead to an irregular variation in the detected matter-wave phase shift. We discuss the nature of this signal and note the problem of distinguishing it from instrumental noise. We also discuss the relation of our experiment to what might be learned by studying the noise in gravitational wave detectors such as LIGO.The paper concludes with a projection that a future search of this nature might be carried out using an atom interferometer in an orbiting satellite. The apparatus is now being constructed

To the theory of the Universe evolution

Self-consistent account of the most simple non-gauge vector fields leads to a broad spectrum of regular scenarios of temporal evolution of the Universe completely within the frames of the Einstein's General relativity. The longitudinal non-gauge vector field is "the missing link in the chain", displaying the repulsive elasticity and allowing the macroscopic description of the main features of the Universe evolution. The singular Big Bang turns into a regular inflation-like state of maximum compression with the further accelerated expansion at late times. The parametric freedom of the theory allows to forget the troubles of fine tuning. In the most interesting cases the analytical solutions of the Einstein's equations are found.Comment: 25 pages, 9figure

Time-Varying Fine-Structure Constant Requires Cosmological Constant

Webb et al. presented preliminary evidence for a time-varying fine-structure constant. We show Teller's formula for this variation to be ruled out within the Einstein-de Sitter universe, however, it is compatible with cosmologies which require a large cosmological constant.Comment: 3 pages, no figures, revtex, to be published in Mod. Phys. Lett.

Identification of Aspergillus Fungal Resistance Factors in a Plant Model System

Aspergillus flavus is a saprophytic, mycotoxigenic fungus that contaminates agriculturally important seeds with the potently toxic and carcinogenic secondary metabolite, aflatoxin. Seed infection by fungi is often prevented by intact seed coats. Although Arabidopsis thaliana is naturally resistant to Aspergillus infection, certain mutants in the flavonoid biosynthetic pathway are compromised in seed coat integrity. We hypothesized that these mutants might also permit Aspergillus infection. To that end, we systematically tested infectibility of mutants in the flavonoid biosynthetic pathway to identify those lacking resistance to Aspergillus fungal infection. Susceptible seeds included those mutated in the genes encoding for synthesis of the first flavonoid pathway precursor, chalcone, through leucocyanidin (CHS, F3’H, and DFR), indicating that the requisite compound is either leucocyanidin or a derivative of that compound. While preliminary observations suggested that older chs seeds might be more susceptible to A. nidulans than younger seeds, an experiment testing infectibility of seeds harvested at specific ages failed to reproduce the infection rates previously observed. Further investigation revealed that chs seed batches dominated by non-viable seeds are more infectible, as expected from a saprophytic fungus. A novel finding was that chs seeds formed during the final weeks of the parent plant’s development are more highly susceptible to A. nidulans. Our results suggest that wildtype Arabidopsis seeds have a barrier to infection, which may be either mechanical or chemical

Experimental Designs for Binary Data in Switching Measurements on Superconducting Josephson Junctions

We study the optimal design of switching measurements of small Josephson junction circuits which operate in the macroscopic quantum tunnelling regime. Starting from the D-optimality criterion we derive the optimal design for the estimation of the unknown parameters of the underlying Gumbel type distribution. As a practical method for the measurements, we propose a sequential design that combines heuristic search for initial estimates and maximum likelihood estimation. The presented design has immediate applications in the area of superconducting electronics implying faster data acquisition. The presented experimental results confirm the usefulness of the method. KEY WORDS: optimal design, D-optimality, logistic regression, complementary log-log link, quantum physics, escape measurement