686 research outputs found
Naturalized species of Cortaderia (Poaceae) in southern Africa
In the past, a single species of Pampas grass, Cortaderia selloana (J.A. & J.J. Schult.) Aschers. & Graebn., was thought to occur in southern Africa. This paper documents the occurrence of a second species (Cortaderia jubata (Lem.) Stapf) which is both more aggressive as an invasive and more frequently encountered than is C. selloana. The species are described and a key for their identification is presented
Mechanical ventilation alters airway nucleotides and purinoceptors in lung and extrapulmonary organs
Extracellular nucleotides are stress-responsive ligands that mediate a variety of cellular processes via purinoceptors. We hypothesized that mechanical ventilation (MV) would alter the extracellular adenyl-nucleotide profile and purinoceptor expression in lung and extrapulmonary tissues. Twenty-eight rats were randomized to: (i) unventilated control animals; (ii) tidal volume (V T; 6 ml/kg); (iii) VT (6 ml/kg) and positive end-expiratory pressure (PEEP; 5 cm H2O); (iv) VT (12 ml/kg); or (v) VT (12 ml/kg) and PEEP (5 cm H2O). Bronchoalveolar lavage (BAL) was analyzed for adenyl-nucleotides. Pulmonary, hepatic, and renal tissues were assessed for P2Y4, P 2Y6, P2X7, A3, and A 2b receptor expression by real-time reverse transcriptase-polymerase chain reaction and Fas/Fas ligand mRNA was quantified in the lung. MV produced volume-dependent changes in BAL nucleotides; AMP and adenosine increased, whereas ATP and ADP proportions decreased. Large-volume MV increased A 2b mRNA and decreased P2X7 in the lung; mRNA changes in lung Fas ligand paralleled P2X7. PEEP normalized BAL nucleotide profiles and A2b expression. Injurious MV reduced hepatic and renal P2X7 mRNA; PEEP normalized these levels in both tissues. Large-volume MV also decreased renal A2b mRNA. MV alters the BAL adenyl-nucleotide profile and purinoceptor patterns in lung, liver, and kidney. PEEP normalizes the BAL nucleotide profile and receptor patterns in lung and extrapulmonary tissues
Investigation into the mechanisms by which microwave heating enhances separation of water-in-oil emulsions
The separation of water-in-oil emulsions made with Azeri crude was investigated using natural gravity settling and microwave heating techniques. Separation times could be reduced by an order of magnitude compared with untreated emulsions. Increasing the salinity of the water phase leads to a 15% average decrease in the settling time for untreated emulsions compared with over 90% for microwave-heated emulsions. An image analysis technique showed that the observed increases in settling time could not be attributed to changes in viscosity alone. Significant coalescence of water droplets occurs during microwave heating, however the effects of coalescence and viscosity reduction cannot be completely decoupled. Despite this, it is clear that it is the thermal effect of microwave heating that leads to improvements in settling times, and that any advantages in microwave heating over conventional heating can be explained by selective heating of the aqueous phase rather than so-called non-thermal effects
Occupational therapy for adults with problems in activities of daily living after stroke
No abstract available
Deterministically Driven Avalanche Models of Solar Flares
We develop and discuss the properties of a new class of lattice-based
avalanche models of solar flares. These models are readily amenable to a
relatively unambiguous physical interpretation in terms of slow twisting of a
coronal loop. They share similarities with other avalanche models, such as the
classical stick--slip self-organized critical model of earthquakes, in that
they are driven globally by a fully deterministic energy loading process. The
model design leads to a systematic deficit of small scale avalanches. In some
portions of model space, mid-size and large avalanching behavior is scale-free,
being characterized by event size distributions that have the form of
power-laws with index values, which, in some parameter regimes, compare
favorably to those inferred from solar EUV and X-ray flare data. For models
using conservative or near-conservative redistribution rules, a population of
large, quasiperiodic avalanches can also appear. Although without direct
counterparts in the observational global statistics of flare energy release,
this latter behavior may be relevant to recurrent flaring in individual coronal
loops. This class of models could provide a basis for the prediction of large
solar flares.Comment: 24 pages, 11 figures, 2 tables, accepted for publication in Solar
Physic
Radio Observations of the January 20, 2005 X-Class Event
We present a multi-frequency and multi-instrument study of the 20 January
2005 event. We focus mainly on the complex radio signatures and their
association with the active phenomena taking place: flares, CMEs, particle
acceleration and magnetic restructuring. As a variety of energetic particle
accelerators and sources of radio bursts are present, in the flare-ejecta
combination, we investigate their relative importance in the progress of this
event. The dynamic spectra of {Artemis-IV-Wind/Waves-Hiras with 2000 MHz-20 kHz
frequency coverage, were used to track the evolution of the event from the low
corona to the interplanetary space; these were supplemented with SXR, HXR and
gamma-ray recordings. The observations were compared with the expected radio
signatures and energetic-particle populations envisaged by the {Standard
Flare--CME model and the reconnection outflow termination shock model. A proper
combination of these mechanisms seems to provide an adequate model for the
interpretation of the observational data.Comment: Accepted for publication in Solar Physic
Quantum spin systems at positive temperature
We develop a novel approach to phase transitions in quantum spin models based
on a relation to their classical counterparts. Explicitly, we show that
whenever chessboard estimates can be used to prove a phase transition in the
classical model, the corresponding quantum model will have a similar phase
transition, provided the inverse temperature and the magnitude of the
quantum spins \CalS satisfy \beta\ll\sqrt\CalS. From the quantum system we
require that it is reflection positive and that it has a meaningful classical
limit; the core technical estimate may be described as an extension of the
Berezin-Lieb inequalities down to the level of matrix elements. The general
theory is applied to prove phase transitions in various quantum spin systems
with \CalS\gg1. The most notable examples are the quantum orbital-compass
model on and the quantum 120-degree model on which are shown to
exhibit symmetry breaking at low-temperatures despite the infinite degeneracy
of their (classical) ground state.Comment: 47 pages, version to appear in CMP (style files included
Excess Mortality in the Aftermath of Hurricane Katrina: A Preliminary Report.
Global Challenges (FGGA
New insights into microwave pyrolysis of biomass: preparation of carbon-based products from pecan nutshells and their application in wastewater treatment
Microwave pyrolysis of pecan nutshell (Carya illinoinensis) biomass was used to produce carbon-based solid products with potential application in contaminated water treatment.
A range of analytical techniques were applied to characterize the intermediate products of microwave pyrolysis in order to monitor the physio-chemical effects of the interacting energy on the biomass.
The performance of the carbon-based products was tested through evaluation of lead ion removal capacity from solution. Further analyses demonstrated that ion-exchange by calcium ions on the material surface was the main mechanism involved in lead removal. Calcium compound development was directly correlated to the interaction of the electromagnetic waves with the biomass.
Through monitoring the physio-chemical effects of biomass-microwave interactions during microwave pyrolysis, we have shown for the first time that the intermediate products differ from those of conventional pyrolysis. We hypothesise that selective heating leads to the (hemi)cellulosic and lignin degradation processes occurring simultaneously, whereas they are largely sequential in conventional pyrolysis.
This work provides optimization parameters essential for the large scale design of microwave processes for this application as well as an understanding of how the operating parameters impact on functionality of the resulting carbon-based materials
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