2,497 research outputs found
Arbuscular Mycorrhizae Occur in Common Spartina Species
We report the presence of arbuscular mycorrhizae (AM) in Spartina alterniflora Loisel roots. Roots were sampled for AM in field-collected and greenhouse-maintained Spartina patens (Aiton) Muhl. and S. alterniflora, the dominant species of Louisianaâs brackish and saline marshes, respectively. Previous reports of AM association in these Spartina sp. are limited and conflicting. Field-collected S. alterniflora had minimal AM (2.4%), whereas 39.5% of the S. patens roots examined were AM colonized. Greenhouse conditions of reduced salinity [3 parts per thousand (ppt)] appeared to increase AM association for S. patens compared with field samples. AM occurrence varied significantly among the three sample sites. Our results of low AM association in S. alterniflora differ from previous studies and confirm one previous report of AM in S. patens. Confirming AM association previously thought to be nonexistent in S. alterniflora marshes is a necessary first step in determining if AM influence zonation and competition
RESPOND â A patient-centred program to prevent secondary falls in older people presenting to the emergency department with a fall: Protocol for a multi-centre randomised controlled trial
Introduction: Participation in falls prevention activities by older people following presentation to the Emergency Department (ED) with a fall is suboptimal. This randomised controlled trial (RCT) will test the RESPOND program which is designed to improve older personsâ participation in falls prevention activities through delivery of patient-centred education and behaviour change strategies. Design and setting: An RCT at two tertiary referral EDs in Melbourne and Perth, Australia. Participants: Five-hundred and twenty eight community-dwelling people aged 60-90 years presenting to the ED with a fall and discharged home will be recruited. People who: require an interpreter or hands-on assistance to walk; live in residential aged care or >50 kilometres from the trial hospital; have terminal illness, cognitive impairment, documented aggressive behaviour or history of psychosis; are receiving palliative care; or are unable to use a telephone will be excluded. Methods: Participants will be randomly allocated to the RESPOND intervention or standard care control group. RESPOND incorporates: (1) home-based risk factor assessment; (2) education, coaching, goal setting, and follow-up telephone support for management of one or more of four risk factors with evidence of effective intervention; and (3) healthcare provider communication and community linkage delivered over six months. Primary outcomes are falls and fall injuries per-person-year. Discussion: RESPOND builds on prior falls prevention learnings and aims to help individuals make guided decisions about how they will manage their falls risk. Patient-centred models have been successfully trialled in chronic and cardiovascular disease however evidence to support this approach in falls prevention is limited. Trial registration. The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684)
Detection of H2D+ in a massive prestellar core in Orion B
Aims. The purpose of this study is to examine the prediction that the deuterated H3+ ion, H2D+, can be found exclusively in the coldest regions of molecular cloud cores. This is also a feasibility study for the detection of the ground-state line of ortho-H2D+ at 372 GHz with APEX. Methods. The 1(10)-1(11) transition of H2D+ at 372 GHz was searched towards selected positions in the massive star forming cloud OriB9, in the dark cloud L183, and in the low- to intermediate mass star-forming cloud R CrA. Results. The line was detected in cold, prestellar cores in the regions of OriB9 and L183, but only upper limits were obtained towards other locations which either have elevated temperatures or contain a newly born star. The H2D+ detection towards OriB9 is the first one in a massive star-forming region. The fractional ortho-H2D+ abundances (relative to H2) are estimated to be about 1.0E-10 in two cold cores in OriB9, and 3.0E-10 in the cold core of L183. Conclusions. The H2D+ detection in OriB9 shows that also massive star forming regions contain very cold prestellar cores which probably have reached matured chemical composition characterized, e.g., by a high degree of deuterium fractionation. Besides as a tracer of the interior parts of prestellar cores, H2D+ may therefore be used to put contraints on the timescales related to massive star formation
Recommended from our members
Low density molecular gas in the galaxy
The distributions and physical conditions in molecular gas in the interstellar medium have been investigated in both the Galaxy and towards external galaxies. For example, Galactic plane surveys in the CO J =1-0 line with the Columbia 1.2-m telescope and with the Five College Radio Astronomy Observatory (FCRAO) 14-m telescopes have been able to trace spiral arms more clearly than HI surveys have been able to reveal, and indicate that most of molecular mass is contained in Giant Molecular Clouds (GMCs). Extensive maps of the whole Milky Way showed two prominent features, the 4-kpc molecular ring and the Galactic center. The physical conditions in the Galaxy have been studied by comparing the intensity of CO J =1-0 line with those of other lines, e.g., 13CO J =1-0, higher J transitions of CO, and dense gas tracers such as HCO+, CS, and HCN.
Previous studies were however strongly biased towards regions where CO emission was known to be intense. The radial distribution of molecular hydrogen shows that most of the H2 gas which is indirectly traced by observations of its associated CO emission, originates from the inner Galaxy (Dame 1993). Extending outwards from a galacto-centric distance of ~7 kpc, the H2 mass surface density decreases dramatically, and HI dominates over H2 in the outer Galaxy. What are physical conditions of molecular gas where the CO emission is relatively weak, and can we really trace all of the molecular gas through obervations of CO? These kinds of problems have not been solved yet, but are addressed in our study
Anatomy of the Soft-Photon Approximation in Hadron-Hadron Bremsstrahlung
A modified Low procedure for constructing soft-photon amplitudes has been
used to derive two general soft-photon amplitudes, a two-s-two-t special
amplitude and a two-u-two-t special amplitude
, where s, t and u are the Mandelstam variables.
depends only on the elastic T-matrix evaluated at four sets
of (s,t) fixed by the requirement that the amplitude be free of derivatives
(T/s and /or T/). Likewise
depends only on the elastic T-matrix evaluated at four sets
of (u,t). In deriving these amplitudes, we impose the condition that
and reduce to and
, respectively, their tree level approximations. The
amplitude represents photon emission from a sum of
one-particle t-channel exchange diagrams and one-particle s-channel exchange
diagrams, while the amplitude represents photon
emission from a sum of one-particle t-channel exchange diagrams and
one-particle u-channel exchange diagrams. The precise expressions for
and are determined by using the
radiation decomposition identities of Brodsky and Brown. We point out that it
is theoretically impossible to describe all bremsstrahlung processes by using
only a single class of soft-photon amplitudes. At least two different classes
are required: the amplitudes which depend on s and t or the amplitudes which
depend on u and t. When resonance effects are important, the amplitude
, not , should be used. For processes with
strong u-channel exchange effects, the amplitude should be
the first choice.Comment: 49 pages report # LA-UR-92-270
Structural and Functional Dynamics of Staphylococcus aureus Biofilms and Biofilm Matrix Proteins on Different Clinical Materials
Medical device-associated staphylococcal infections are a common and challenging problem. However, detailed knowledge of staphylococcal biofilm dynamics on clinically relevant surfaces is still limited. In the present study, biofilm formation of the Staphylococcus aureus ATCC 25923 strain was studied on clinically relevant materialsâborosilicate glass, plexiglass, hydroxyapatite, titanium and polystyreneâat 18, 42 and 66 h. Materials with the highest surface roughness and porosity (hydroxyapatite and plexiglass) did not promote biofilm formation as efficiently as some other selected materials. Matrix-associated poly-N-acetyl-ÎČ-(1-6)-glucosamine (PNAG) was considered important in young (18 h) biofilms, whereas proteins appeared to play a more important role at later stages of biofilm development. A total of 460 proteins were identified from biofilm matrices formed on the indicated materials and time pointsâfrom which, 66 proteins were proposed to form the core surfaceome. At 18 h, the appearance of several r-proteins and glycolytic adhesive moonlighters, possibly via an autolysin (AtlA)-mediated release, was demonstrated in all materials, whereas classical surface adhesins, resistance- and virulence-associated proteins displayed greater variation in their abundances depending on the used material. Hydroxyapatite-associated biofilms were more susceptible to antibiotics than biofilms formed on titanium, but no clear correlation between the tolerance and biofilm age was observed. Thus, other factors, possibly the adhesive moonlighters, could have contributed to the observed chemotolerant phenotype. In addition, a protein-dependent matrix network was observed to be already well-established at the 18 h time point. To the best of our knowledge, this is among the first studies shedding light into matrix-associated surfaceomes of S. aureus biofilms grown on different clinically relevant materials and at different time points
Coloured peak algebras and Hopf algebras
For a finite abelian group, we study the properties of general
equivalence relations on G_n=G^n\rtimes \SG_n, the wreath product of with
the symmetric group \SG_n, also known as the -coloured symmetric group. We
show that under certain conditions, some equivalence relations give rise to
subalgebras of \k G_n as well as graded connected Hopf subalgebras of
\bigoplus_{n\ge o} \k G_n. In particular we construct a -coloured peak
subalgebra of the Mantaci-Reutenauer algebra (or -coloured descent algebra).
We show that the direct sum of the -coloured peak algebras is a Hopf
algebra. We also have similar results for a -colouring of the Loday-Ronco
Hopf algebras of planar binary trees. For many of the equivalence relations
under study, we obtain a functor from the category of finite abelian groups to
the category of graded connected Hopf algebras. We end our investigation by
describing a Hopf endomorphism of the -coloured descent Hopf algebra whose
image is the -coloured peak Hopf algebra. We outline a theory of
combinatorial -coloured Hopf algebra for which the -coloured
quasi-symmetric Hopf algebra and the graded dual to the -coloured peak Hopf
algebra are central objects.Comment: 26 pages latex2
Looking for the S-Z Effect towards Distant ROSAT Clusters of Galaxies
We report on observations of the Sunyaev-Zeldovich effect towards X-ray ROSAT
clusters taken with a double channel (1.2 and 2 mm) photometer installed at the
focus of the 15m SEST antenna in Chile. This paper describes the first results
obtained for the high-z clusters S1077, A2744 and S295. Marginal detections
were found for A2744 and at 1 mm for S1077. We discuss these data in terms of
contamination of sources along the line of sight and give a constraint on the
amplitude of the kinematic effect.Comment: 17 pg Latex file (using aasms4.sty) gzip'd tar'd uuencoded file
including 1 ps figure, ApJ Letter in pres
Evidence of a new state in Be observed in the Li -decay
Coincidences between charged particles emitted in the -decay of
Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in Be has been identified selecting the +
He + He+n channel. The angular correlations between the
particle and the center of mass of the He+n system favors spin and
parity assignment of 3/2 for this state as well as for the previously known
state at 18 MeV.Comment: 13 pages, 6 figure
- âŠ