Precision absolute positional measurement of laser beams

We describe an instrument which, coupled with a suitable coordinate measuring machine, facilitates the absolute measurement within the machine frame of the propagation direction of a millimeter-scale laser beam to an accuracy of around ±4  μm in position and ±20  μrad in angle

Bar shoes and ambient temperature are risk factors for exercise-induced pulmonary haemorrhage in Thoroughbred racehorses

Reasons for performing study Ambient temperature has been identified as a risk factor for exercise-induced pulmonary haemorrhage (EIPH) in racing Thoroughbreds. This warranted a more expansive investigation of climatic conditions on the incidence and severity of EIPH. The impact of other variables such as the type of bit used, tongue ties and nonstandard shoes has not been reported and also warrant investigation. Objectives To examine the effect of various climatic variables as contributing risk factors for EIPH. Other previously uninvestigated variables as well as standard track and population factors will also be examined. Study design Cross-sectional study. Methods Thoroughbred racehorses competing at metropolitan racetracks in Perth, Western Australia were examined 30–200 min post race with tracheobronchoscopy. Examination took place at 48 race meetings over a 12 month period. Examinations were graded (0–4), independently by two experienced veterinarians. Univariable analyses were performed and variables with a P<0.25 were entered into a multivariable logistic regression analysis. The analysis was performed twice using the presence of blood (EIPH grade 0 vs. grades ≥1) and EIPH grades ≤1 vs. EIPH grades ≥2 as dependent variables. Results Exercise-induced pulmonary haemorrhage was diagnosed in 56.6% of observations. Lower ambient temperature was significantly associated with EIPH grades ≥1 (OR 0.95; 95% CI 0.93–0.98) and EIPH grades ≥2 (OR 0.97; 95% CI 0.94–1.0). Bar shoes were significantly associated with EIPH grades ≥1 (OR 6.35; 95% CI 2.17–18.54) and EIPH grades ≥2 (OR 2.72; 95% CI 1.3–5.68). Increasing race distance was significantly associated with EIPH grade ≥1 and increasing lifetime starts was significantly associated with EIPH grade ≥2. Conclusions Ambient temperature is a risk factor for EIPH in Thoroughbred racehorses, with lower temperatures associated with increased risk. Bar shoes are a novel risk factor for EIPH in this population

A simulated study of implicit feedback models

In this paper we report on a study of implicit feedback models for unobtrusively tracking the information needs of searchers. Such models use relevance information gathered from searcher interaction and can be a potential substitute for explicit relevance feedback. We introduce a variety of implicit feedback models designed to enhance an Information Retrieval (IR) system's representation of searchers' information needs. To benchmark their performance we use a simulation-centric evaluation methodology that measures how well each model learns relevance and improves search effectiveness. The results show that a heuristic-based binary voting model and one based on Jeffrey's rule of conditioning [5] outperform the other models under investigation

Using the quantum probability ranking principle to rank interdependent documents

A known limitation of the Probability Ranking Principle (PRP) is that it does not cater for dependence between documents. Recently, the Quantum Probability Ranking Principle (QPRP) has been proposed, which implicitly captures dependencies between documents through “quantum interference”. This paper explores whether this new ranking principle leads to improved performance for subtopic retrieval, where novelty and diversity is required. In a thorough empirical investigation, models based on the PRP, as well as other recently proposed ranking strategies for subtopic retrieval (i.e. Maximal Marginal Relevance (MMR) and Portfolio Theory(PT)), are compared against the QPRP. On the given task, it is shown that the QPRP outperforms these other ranking strategies. And unlike MMR and PT, one of the main advantages of the QPRP is that no parameter estimation/tuning is required; making the QPRP both simple and effective. This research demonstrates that the application of quantum theory to problems within information retrieval can lead to significant improvements

Metric trees of generalized roundness one

Every finite metric tree has generalized roundness strictly greater than one. On the other hand, some countable metric trees have generalized roundness precisely one. The purpose of this paper is to identify some large classes of countable metric trees that have generalized roundness precisely one. At the outset we consider spherically symmetric trees endowed with the usual combinatorial metric (SSTs). Using a simple geometric argument we show how to determine decent upper bounds on the generalized roundness of finite SSTs that depend only on the downward degree sequence of the tree in question. By considering limits it follows that if the downward degree sequence $(d_{0}, d_{1}, d_{2}...)$ of a SST $(T,\rho)$ satisfies $|\{j \, | \, d_{j} > 1 \}| = \aleph_{0}$, then $(T,\rho)$ has generalized roundness one. Included among the trees that satisfy this condition are all complete $n$-ary trees of depth $\infty$ ($n \geq 2$), all $k$-regular trees ($k \geq 3$) and inductive limits of Cantor trees. The remainder of the paper deals with two classes of countable metric trees of generalized roundness one whose members are not, in general, spherically symmetric. The first such class of trees are merely required to spread out at a sufficient rate (with a restriction on the number of leaves) and the second such class of trees resemble infinite combs.Comment: 14 pages, 2 figures, 2 table

An Automated System for Hydroxide Catalysis Bonding of Precision-Aligned Optical Systems

Precision-aligned, robust, ultra-stable optical assemblies are required in an increasing number of space-based applications such as fundamental science, metrology and geodesy. Hydroxide catalysis bonding is a proven, glue-free, technology for building such optical systems from materials such as ULE, Zerodur and fused silica. Hydroxide catalysis bonded optical systems have flown in missions such as GP-B and LISA Pathfinder achieving picometer path-length stability and microradian component stability over full mission lifetime. Component alignment and bonding was previously a largely manual process that required skilled operators and significant time. We have recently automated most of the alignment and bonding steps with the goals of improving overall precision, speed and reliability. Positioning and bonding of an optical component to within 4 microns and 10 microradians of a target position and alignment can now be reliably completed within half an hour, compared to the many hours typically taken previously. The key new features of this system are an interferometer that monitors the parallelism and separation of the surfaces to be bonded and a precision multi-axis manipulator that can optimise component alignment as it brings it down to the point of bonding. We present a description of the system and a summary of the alignment results obtained in a series of 9 test bonds. We also show how this system is being developed for integration into a precision optical manufacturing facility for assembly of large optical systems

Is there an association between airborne and surface microbes in the critical care environment?

BackgroundThere are few data and no accepted standards for air quality in the intensive care unit (ICU). Any relationship between airborne pathogens and hospital-acquired infection (HAI) risk in the ICU remains unknown.AimFirst, to correlate environmental contamination of air and surfaces in the ICU; second, to examine any association between environmental contamination and ICU-acquired staphylococcal infection.MethodsPatients, air, and surfaces were screened on 10 sampling days in a mechanically ventilated 10-bed ICU for a 10-month period. Near-patient hand-touch sites (N = 500) and air (N = 80) were screened for total colony count and Staphylococcus aureus. Air counts were compared with surface counts according to proposed standards for air and surface bioburden. Patients were monitored for ICU-acquired staphylococcal infection throughout.FindingsOverall, 235 of 500 (47%) surfaces failed the standard for aerobic counts (≤2.5 cfu/cm2). Half of passive air samples (20/40: 50%) failed the ‘index of microbial air’ contamination (2 cfu/9 cm plate/h), and 15/40 (37.5%) active air samples failed the clean air standard

Ab-initio simulations on growth and interface properties of epitaxial oxides on silicon

The replacement of SiO2 by so-called high-k oxides is one of the major challenges for the semiconductor industry to date. Based on electronic structure calculations and ab-initio molecular dynamics simulations, we are able to provide a consistent picture of the growth process of a class of epitaxial oxides around SrO and SrTiO3. The detailed understanding of the interfacial binding principles has also allowed us to propose a way to engineer the band-offsets between the oxide and the silicon substrate.Comment: 6 pages, 6 figures, proceeding for the INFOS2005 conference (http://www.imec.be/infos/

Gravitation and inertia; a rearrangement of vacuum in gravity

We address the gravitation and inertia in the framework of 'general gauge principle', which accounts for 'gravitation gauge group' generated by hidden local internal symmetry implemented on the flat space. We connect this group to nonlinear realization of the Lie group of 'distortion' of local internal properties of six-dimensional flat space, which is assumed as a toy model underlying four-dimensional Minkowski space. The agreement between proposed gravitational theory and available observational verifications is satisfactory. We construct relativistic field theory of inertia and derive the relativistic law of inertia. This theory furnishes justification for introduction of the Principle of Equivalence. We address the rearrangement of vacuum state in gravity resulting from these ideas.Comment: 17 pages, no figures, revtex4, Accepted for publication in Astrophys. Space Sc