Flight performance of a navigation, guidance, and control system concept for automatic approach and landing of space shuttle orbiter

Unpowered automatic approaches and landings were conducted to study navigation, guidance, and control problems associated with terminal area approach and landing for the space shuttle vehicle. The flight tests were performed in a Convair 990 aircraft equipped with a digital flight control computer connected to the aircraft control system and displays. The tests were designed to evaluate the performance of a navigation and guidance concept that utilized blended radio/inertial navigation with VOR, DME, and ILS as the ground navigation aids. Results from 36 automatic approaches and landings from 11,300 m (37,000 ft) to touchdown are presented. Preliminary results indicate that this concept may provide sufficient accuracy to accomplish automatic landing of the shuttle orbiter without air-breathing engines

Generic model of an atom laser

We present a generic model of an atom laser by including a pump and loss term in the Gross-Pitaevskii equation. We show that there exists a threshold for the pump above which the mean matter field assumes a non-vanishing value in steady-state. We study the transient regime of this atom laser and find oscillations around the stationary solution even in the presence of a loss term. These oscillations are damped away when we introduce a position dependent loss term. For this case we present a modified Thomas-Fermi solution that takes into account the pump and loss. Our generic model of an atom laser is analogous to the semi-classical theory of the laser.Comment: 15 pages, including 5 figures, submitted to Phys. Rev. A, revised manuscript, file also available at http://www.physik.uni-ulm.de/quan/users/kne

The truth about metagenomics: quantifying and counteracting bias in 16S rRNA studies

Background Characterizing microbial communities via next-generation sequencing is subject to a number of pitfalls involving sample processing. The observed community composition can be a severe distortion of the quantities of bacteria actually present in the microbiome, hampering analysis and threatening the validity of conclusions from metagenomic studies. We introduce an experimental protocol using mock communities for quantifying and characterizing bias introduced in the sample processing pipeline. We used 80 bacterial mock communities comprised of prescribed proportions of cells from seven vaginally-relevant bacterial strains to assess the bias introduced in the sample processing pipeline. We created two additional sets of 80 mock communities by mixing prescribed quantities of DNA and PCR product to quantify the relative contribution to bias of (1) DNA extraction, (2) PCR amplification, and (3) sequencing and taxonomic classification for particular choices of protocols for each step. We developed models to predict the “true” composition of environmental samples based on the observed proportions, and applied them to a set of clinical vaginal samples from a single subject during four visits. Results We observed that using different DNA extraction kits can produce dramatically different results but bias is introduced regardless of the choice of kit. We observed error rates from bias of over 85% in some samples, while technical variation was very low at less than 5% for most bacteria. The effects of DNA extraction and PCR amplification for our protocols were much larger than those due to sequencing and classification. The processing steps affected different bacteria in different ways, resulting in amplified and suppressed observed proportions of a community. When predictive models were applied to clinical samples from a subject, the predicted microbiome profiles were better reflections of the physiology and diagnosis of the subject at the visits than the observed community compositions. Conclusions Bias in 16S studies due to DNA extraction and PCR amplification will continue to require attention despite further advances in sequencing technology. Analysis of mock communities can help assess bias and facilitate the interpretation of results from environmental samples

Structural Phase Transition at High Temperatures in Solid Molecular Hydrogen and Deuterium

We study the effect of temperature up to 1000K on the structure of dense molecular para-hydrogen and ortho-deuterium, using the path-integral Monte Carlo method. We find a structural phase transition from orientationally disordered hexagonal close packed (hcp) to an orthorhombic structure of Cmca symmetry before melting. The transition is basically induced by thermal fluctuations, but quantum fluctuations of protons (deuterons) are important in determining the transition temperature through effectively hardening the intermolecular interaction. We estimate the phase line between hcp and Cmca phases as well as the melting line of the Cmca solid.Comment: 8 pages, 7 figures; accepted in Phys. Rev.

Evolution of the Scale Factor with a Variable Cosmological Term

Evolution of the scale factor a(t) in Friedmann models (those with zero pressure and a constant cosmological term Lambda) is well understood, and elegantly summarized in the review of Felten and Isaacman [Rev. Mod. Phys. 58, 689 (1986)]. Developments in particle physics and inflationary theory, however, increasingly indicate that Lambda ought to be treated as a dynamical quantity. We revisit the evolution of the scale factor with a variable Lambda-term, and also generalize the treatment to include nonzero pressure. New solutions are obtained and evaluated using a variety of observational criteria. Existing arguments for the inevitability of a big bang (ie., an initial state with a=0) are substantially weakened, and can be evaded in some cases with Lambda_0 (the present value of Lambda) well below current experimental limits.Comment: 29 pages, 12 figures (not included), LaTeX, uses Phys Rev D style files (revtex.cls, revtex.sty, aps.sty, aps10.sty, prabib.sty). To appear in Phys Rev

Regularity Properties and Pathologies of Position-Space Renormalization-Group Transformations

We reconsider the conceptual foundations of the renormalization-group (RG) formalism, and prove some rigorous theorems on the regularity properties and possible pathologies of the RG map. Regarding regularity, we show that the RG map, defined on a suitable space of interactions (= formal Hamiltonians), is always single-valued and Lipschitz continuous on its domain of definition. This rules out a recently proposed scenario for the RG description of first-order phase transitions. On the pathological side, we make rigorous some arguments of Griffiths, Pearce and Israel, and prove in several cases that the renormalized measure is not a Gibbs measure for any reasonable interaction. This means that the RG map is ill-defined, and that the conventional RG description of first-order phase transitions is not universally valid. For decimation or Kadanoff transformations applied to the Ising model in dimension $d \ge 3$, these pathologies occur in a full neighborhood $\{ \beta > \beta_0 ,\, |h| < \epsilon(\beta) \}$ of the low-temperature part of the first-order phase-transition surface. For block-averaging transformations applied to the Ising model in dimension $d \ge 2$, the pathologies occur at low temperatures for arbitrary magnetic-field strength. Pathologies may also occur in the critical region for Ising models in dimension $d \ge 4$. We discuss in detail the distinction between Gibbsian and non-Gibbsian measures, and give a rather complete catalogue of the known examples. Finally, we discuss the heuristic and numerical evidence on RG pathologies in the light of our rigorous theorems.Comment: 273 pages including 14 figures, Postscript, See also ftp.scri.fsu.edu:hep-lat/papers/9210/9210032.ps.

The context influences doctors' support of shared decision-making in cancer care

Most cancer patients in westernised countries now want all information about their situation, good or bad, and many wish to be involved in decision-making. The attitudes to and use of shared decision-making (SDM) by cancer doctors is not well known. Australian cancer clinicians treating breast, colorectal, gynaecological, haematological, or urological cancer were surveyed to identify their usual approach to decision-making and their comfort with different decision-making styles when discussing treatment with patients. A response rate of 59% resulted in 624 complete surveys, which explored usual practice in discussing participation in decision-making, providing information, and perception of the role patients want to play. Univariate and multivariate analyses were performed to identify predictors of use of SDM. Most cancer doctors (62.4%) reported using SDM and being most comfortable with this approach. Differences were apparent between reported high comfort with SDM and less frequent usual practice. Multivariate analysis showed that specialisation in breast or urological cancers compared to other cancers (AOR 3.02), high caseload of new patients per month (AOR 2.81) and female gender (AOR 1.87) were each independently associated with increased likelihood of use of SDM. Barriers exist to the application of SDM by doctors according to clinical situation and clinician characteristics

Post-treatment skin reactions reported by cancer patients differ by race, not by treatment or expectations

Cancer patients may experience skin problems while undergoing chemotherapy and radiation therapy. Frequency of skin reactions may be influenced by skin pigmentation and psychological factors. A Symptom Inventory completed by 656 cancer patients nationwide before and after chemotherapy, radiation therapy, or chemotherapy plus radiation therapy was analysed to determine if treatment type, race (Black vs White), and pretreatment expectations influenced post-treatment skin reactions. Subsequent analysis of a local Symptom Inventory completed weekly for 5 weeks by 308 patients receiving radiation therapy examined severity of reported skin reactions. Significantly more patients receiving radiation therapy had stronger expectations of skin problems (62%) than patients receiving chemotherapy (40%, P=0.001) or chemotherapy plus radiation therapy (45%, P=0.003). Overall, expectations did not correlate with patient reported post-treatment skin problems in white (r=0.014, P=0.781) or black (r=0.021, P=0.936) patients. Although no significant difference was found between black and white patients in their pretreatment expectations of skin problems (P=0.32), black patients (10 out of 18, 56%) reported more skin problems than white patients (90 out of 393, 23%, P=0.001). Similarly, the local study showed that significantly more black patients (1 out of 5, 20%) reported severe skin reactions at the treatment site than white patients (12 out of 161, 8%). A direct correlation was observed between severity of skin problems and pain at the treatment site (r=0.541, P<0.001). Total radiation exposure did not significantly correlate with the report of skin problems at the treatment site for white or black patients. Overall, black patients reported more severe post-treatment skin problems than white patients. Our results suggest that symptom management for post-treatment skin reactions in cancer patients receiving radiation treatment could differ depending on their racial background