3,971 research outputs found
Impact of wild-type and genetically modified Pseudomonas fluorescens on soil enzyme activities and microbial population structure in the rhizosphere of pea
The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-294x.1998.00367.xThe aim of this work was to determine the impact of wild type along with functionally and non-functionally modified Pseudomonas fluorescens strains in the rhizosphere. The wild type F113 strain carried a gene encoding the production of the antibiotic 2,4 diacetylphloroglucinol (DAPG) useful in plant disease control, and was marked with a lacZY gene cassette. The first modified strain was a functional modification of strain F113 with repressed production of DAPG, creating the DAPG negative strain F113 G22. The second paired comparison was a non-functional modification of wild type (unmarked) strain SBW25, constructed to carry marker genes only, creating strain SBW25 EeZY-6KX. Significant perturbations were found in the indigenous bacterial population structure, with the F113, (DAPG+) strain causing a shift towards slower growing colonies (K strategists) compared with the non-antibiotic producing derivative (F113 G22) and the SBW25 strains. The DAPG+ strain also significantly reduced, in comparison with the other inocula, the total Pseudomonas populations but did not affect the total microbial populations. The survival of F113 and F113 G22 were an order of magnitude lower than the SBW 25 strains. The DAPG+ strain caused a significant decrease in the shoot to root ratio in comparison to the control and other inoculants, indicating plant stress. F113 increased soil alkaline phosphatase, phosphodiesterase and aryl sulphatase activities compared to the other inocula, which themselves reduced the same enzyme activities compared to the control. In contrast to this, the -glucosidase, -galactosidase and N-acetyl glucosaminidase activities decreased with the inoculation of the DAPG+ strain. These results indicate that soil enzymes are sensitive to the impact of GMM inoculation.Peer reviewe
Collaborative Computation in Self-Organizing Particle Systems
Many forms of programmable matter have been proposed for various tasks. We
use an abstract model of self-organizing particle systems for programmable
matter which could be used for a variety of applications, including smart paint
and coating materials for engineering or programmable cells for medical uses.
Previous research using this model has focused on shape formation and other
spatial configuration problems (e.g., coating and compression). In this work we
study foundational computational tasks that exceed the capabilities of the
individual constant size memory of a particle, such as implementing a counter
and matrix-vector multiplication. These tasks represent new ways to use these
self-organizing systems, which, in conjunction with previous shape and
configuration work, make the systems useful for a wider variety of tasks. They
can also leverage the distributed and dynamic nature of the self-organizing
system to be more efficient and adaptable than on traditional linear computing
hardware. Finally, we demonstrate applications of similar types of computations
with self-organizing systems to image processing, with implementations of image
color transformation and edge detection algorithms
Posterior-based proposals for speeding up Markov chain Monte Carlo
Markov chain Monte Carlo (MCMC) is widely used for Bayesian inference in
models of complex systems. Performance, however, is often unsatisfactory in
models with many latent variables due to so-called poor mixing, necessitating
development of application specific implementations. This paper introduces
"posterior-based proposals" (PBPs), a new type of MCMC update applicable to a
huge class of statistical models (whose conditional dependence structures are
represented by directed acyclic graphs). PBPs generates large joint updates in
parameter and latent variable space, whilst retaining good acceptance rates
(typically 33%). Evaluation against other approaches (from standard Gibbs /
random walk updates to state-of-the-art Hamiltonian and particle MCMC methods)
was carried out for widely varying model types: an individual-based model for
disease diagnostic test data, a financial stochastic volatility model, a mixed
model used in statistical genetics and a population model used in ecology.
Whilst different methods worked better or worse in different scenarios, PBPs
were found to be either near to the fastest or significantly faster than the
next best approach (by up to a factor of 10). PBPs therefore represent an
additional general purpose technique that can be usefully applied in a wide
variety of contexts.Comment: 54 pages, 11 figures, 2 table
Social problems in oncology
A study was undertaken to describe, evaluate and categorise the social problems experienced by cancer patients. Ninety-six adult cancer patients at all stages of disease participated in either a telephone focus group discussion, a face to face focus group or an individual interview which were tape recorded and transcribed. Six experts analysed the transcripts. A total of 32 social problems were identified categorized under eight headings plus four single items. The categories were: problems with (1) managing in the home, (2) health and welfare services, (3) finances, (4) employment, (5) legal matters, (6) relationships, (7) sexuality and body image and (8) recreation. Problems with relationships and communication were the most frequently reported with financial, employment, body image and domestic problems also being widely endorsed. Female groups, younger patient groups and groups where the aim of treatment was palliative reported more social problems than other groups. Social problems are common and important to cancer patients. The social problems identified in this study will contribute to an item pool generated for developing a Social Problems Inventory that may be included in patient centred assessment as part of routine oncology practice
Impact of sports participation on incidence of bone traumatic fractures and health care costs among adolescents: ABCD – Growth Study
This is the author accepted manuscript. The final version is available from Taylor & Francis.Objective: To analyze the risk of bone traumatic fractures according to the engagement in sports, as well as to identify the potential impact of sports participation and traumatic fractures on health care costs among adolescents. Methods: This is a longitudinal 12-months follow-up study of 285 adolescents of both sexes in Brazil. We assessed the occurrence of traumatic fractures and health care services (hospitalizations, medicine use, medical consultations and exams) by phone contact every single month for 12 months. Adolescents were divided into four groups according to sport characteristics: non-sport (n= 104), non-impact sport (swimming [n= 34]), martial arts (n= 49 [judo, karate, kung-Fu]) and impact sports (n= 98 [track-and-field, basketball, gymnastics, tennis, and baseball]). Results: The incidence of new fractures was 2.1%. The overall costs accounted during the 12-month follow-up were U 13.86) had higher health care costs than non-sport (US 2.23) and impact sports (US$ 2.32). Conclusion: swimming seems to be related to higher health care costs among adolescents
Radio Emission from Ultra-Cool Dwarfs
The 2001 discovery of radio emission from ultra-cool dwarfs (UCDs), the very
low-mass stars and brown dwarfs with spectral types of ~M7 and later, revealed
that these objects can generate and dissipate powerful magnetic fields. Radio
observations provide unparalleled insight into UCD magnetism: detections extend
to brown dwarfs with temperatures <1000 K, where no other observational probes
are effective. The data reveal that UCDs can generate strong (kG) fields,
sometimes with a stable dipolar structure; that they can produce and retain
nonthermal plasmas with electron acceleration extending to MeV energies; and
that they can drive auroral current systems resulting in significant
atmospheric energy deposition and powerful, coherent radio bursts. Still to be
understood are the underlying dynamo processes, the precise means by which
particles are accelerated around these objects, the observed diversity of
magnetic phenomenologies, and how all of these factors change as the mass of
the central object approaches that of Jupiter. The answers to these questions
are doubly important because UCDs are both potential exoplanet hosts, as in the
TRAPPIST-1 system, and analogues of extrasolar giant planets themselves.Comment: 19 pages; submitted chapter to the Handbook of Exoplanets, eds. Hans
J. Deeg and Juan Antonio Belmonte (Springer-Verlag
Molecular evolution of HoxA13 and the multiple origins of limbless morphologies in amphibians and reptiles
Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes
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Sports Participation and Health Care Costs in Older Adults Aged 50 Years or Older
Brazilian Ministry of Science and Technology; São Paulo Research Foundatio
Lack of trust in maternal support is associated with negative interpretations of ambiguous maternal behavior
Attachment theory assumes that children who lack trust in maternal availability for support are more inclined to interpret maternal behavior in congruence with their expectation that mother will remain unavailable for support. To provide the first test of this assumption, early adolescents (9-13 years old) were asked to assess whether ambiguous interactions with mother should be interpreted in a positive or a negative way. In our sample (n = 322), results showed that early adolescents' lack of trust in their mother's availability for support was related to more negative interpretations of maternal behavior. The associations remained significant after controlling for depressive mood. The importance of these findings for our understanding of attachment theory, attachment stability, and clinical practice are discussed
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