1,698 research outputs found
Effects of post-fire logging on forest surface air temperatures in the Siskiyou Mountains, Oregon, USA
Following stand-replacing wildfire, post-fire (salvage) logging of fire-killed trees is a widely implemented management practice in many forest types. A common hypothesis is that removal of fire-killed trees increases surface temperatures due to loss of shade and increased solar radiation, thereby influencing vegetation establishment and possibly stand development. Six years after a wildfire in a Mediterranean-climate mixed-conifer forest in southwest Oregon, USA, we measured the effects of post-fire logging (> 90 per cent dead tree (snag) removal) on growing season surface air temperatures. Compared with unlogged severely burned forest, post-fire logging did not lead to increased maximum daily surface air temperature. However, dead tree removal was associated with lower nightly minimum temperatures (similar to 1 degrees C) and earlier daytime heating, leading to a 1-2 degrees C difference during the warming portion of the day. Effects varied predictably by aspect. The patterns reported here represent a similar but muted pattern as previously reported for microclimatic changes following clear-cutting of green trees. Effects of microsites such as tree bases on fine-scale temperature regimes require further investigation
An evaluation of seed drills with various openers for seeding winter wheat in southwest Saskatchewan
Non-Peer ReviewedFour seed drills were evaluated for seeding winter wheat in South West Saskatchewan. Furrow opener types were the Swift Current zero-till offset disc, an air-seeder with Dutch banding knives, the Swift Current zero-till hoe, and Versatile Noble zero-till hoe. Soil disturbance varies from least to greatest in order listed, however, sufficient stubble is retained with all openers to normally ensure winter survival and adequate plant stands. No yield differences were observed for plots seeded by the various drills on chemical fallow on a clay loam soil. There is a tendency for the zero-till disc to show better yield on stubble on a clay loam soil whereas a hoe opener tends to show better yields on stubble for a sandy loam soil. However, other factors such as weather between fall and spring, GSP and spring soil moisture interacting with plant densities appear to affect yields equally as great. More years of data are required to confirm these trends
Defining and investigating difficult asthma: Developing quality indicators
SummaryBackgroundThere is no agreed definition of âdifficult asthmaâ or what investigations should be available to investigate these patients. Patients with difficult asthma remain symptomatic on high levels of treatment and are high users of medical resources.AimTo develop a set of quality indicators for the definition and investigation of difficult asthma.MethodModified RAND Appropriateness Method was used. An expert panel composed of nine hospital asthma specialists who run âdifficultâ asthma clinics and were identified from a shortlist of key workers in the field. Indicators were rated as necessary to define and investigate difficult asthma.ResultsDifficult asthma was defined as âsymptoms persisting beyond therapy consistent with step 4 of the British Thoracic Society (BTS) guidelinesâ (high dose inhaled corticosteroids and long acting ÎČ2-agonists). Eighty-three indicators were identified (40 relating to definition and 43 relating to investigations). Of these 32 (39%) were rated as necessary: 7 out of 40 (18%) for defining difficult asthma and 23 out of 43 (53%) for investigations. Indicators of high medical resource usage were characteristic of the âdifficultâ nature of the management of patient with difficult asthma. A framework for the investigation of these patients was created.ConclusionThe listed performance indicators identify a range of requirements that are necessary to define difficult asthma. Targeting of real needs in this group of patients will lead to better patient care and reduction of âwasteâ in provision of healthcare
Rare -Decays and Heavy to Light Semileptonic Transitions in the Isgur and Wise Limit
From the experimental branching ratios for and
D^+ --> {\overl K}^{*0}({\overl K}^0) e^+ \nu_e one finds, in the Heavy Quark
Limit of , , larger but consistent with
the actual quoted range . In the same framework one predicts
for .Comment: 9 pages, 1 Figure avalaible on request from [email protected]
Objective classification of fabric pilling based on the two-dimensional discrete wavelet transform
A number of methods for automated objective ratings of fabric pilling based on image analysis are described in the literature. The periodic structure of fabrics makes them suitable candidates for frequency domain analysis. We propose a new method of frequency domain analysis based on the two-dimensional discrete wavelet transform to objectively measure pilling intensity in sample images. We present a preliminary evaluation of the proposed method based on analysis of two series of standard pilling evaluation test images. The initial results suggest that the proposed method is feasible, and that the ability of the method to discriminate between levels of pilling intensity depends on the wavelet analysis scale being closely matched to the fabric interyarn pitch. We also present a heuristic method for optimal selection of an analysis wavelet and associated analysis scale. <br /
Dynamics of Simple Balancing Models with State Dependent Switching Control
Time-delayed control in a balancing problem may be a nonsmooth function for a
variety of reasons. In this paper we study a simple model of the control of an
inverted pendulum by either a connected movable cart or an applied torque for
which the control is turned off when the pendulum is located within certain
regions of phase space. Without applying a small angle approximation for
deviations about the vertical position, we see structurally stable periodic
orbits which may be attracting or repelling. Due to the nonsmooth nature of the
control, these periodic orbits are born in various discontinuity-induced
bifurcations. Also we show that a coincidence of switching events can produce
complicated periodic and aperiodic solutions.Comment: 36 pages, 12 figure
Magnetar outbursts: an observational review
Transient outbursts from magnetars have shown to be a key property of their
emission, and one of the main way to discover new sources of this class. From
the discovery of the first transient event around 2003, we now count about a
dozen of outbursts, which increased the number of these strongly magnetic
neutron stars by a third in six years. Magnetar outbursts might involve their
multi-band emission resulting in an increased activity from radio to hard
X-ray, usually with a soft X-ray flux increasing by a factor of 10-1000 with
respect to the quiescent level. A connected X-ray spectral evolution is also
often observed, with a spectral softening during the outburst decay. The flux
decay times vary a lot from source to source, ranging from a few weeks to
several years, as also the decay law which can be exponential-like, a power-law
or even multiple power-laws can be required to model the flux decrease. We
review here on the latest observational results on the multi-band emission of
magnetars, and summarize one by one all the transient events which could be
studied to date from these sources.Comment: 34 pages, 6 figures. Chapter of the Springer Book ASSP 7395
"High-energy emission from pulsars and their systems", proceeding of the Sant
Cugat Forum on Astrophysics (12-16 April 2010). Review updated to January
201
First normal stress difference and crystallization in a dense sheared granular fluid
The first normal stress difference () and the microstructure
in a dense sheared granular fluid of smooth inelastic hard-disks are probed
using event-driven simulations. While the anisotropy in the second moment of
fluctuation velocity, which is a Burnett-order effect, is known to be the
progenitor of normal stress differences in {\it dilute} granular fluids, we
show here that the collisional anisotropies are responsible for the normal
stress behaviour in the {\it dense} limit. As in the elastic hard-sphere
fluids, remains {\it positive} (if the stress is defined in
the {\it compressive} sense) for dilute and moderately dense flows, but becomes
{\it negative} above a critical density, depending on the restitution
coefficient. This sign-reversal of occurs due to the {\it
microstructural} reorganization of the particles, which can be correlated with
a preferred value of the {\it average} collision angle in the direction opposing the shear. We also report on the shear-induced
{\it crystal}-formation, signalling the onset of fluid-solid coexistence in
dense granular fluids. Different approaches to take into account the normal
stress differences are discussed in the framework of the relaxation-type
rheological models.Comment: 21 pages, 13 figure
Cost and costâeffectiveness of a simplified treatment model with directâacting antivirals for chronic hepatitis C in Cambodia
Background & Aims
In 2016, MĂ©decins Sans FrontiĂšres established the first general population Hepatitis C virus (HCV) screening and treatment site in Cambodia, offering free directâacting antiviral (DAA) treatment. This study analysed the costâeffectiveness of this intervention.
Methods
Costs, quality adjusted life years (QALYs) and costâeffectiveness of the intervention were projected with a Markov model over a lifetime horizon, discounted at 3%/year. Patientâlevel resourceâuse and outcome data, treatment costs, costs of HCVârelated healthcare and EQâ5Dâ5L health states were collected from an observational cohort study evaluating the effectiveness of DAA treatment under full and simplified models of care compared to no treatment; other model parameters were derived from literature. Incremental costâeffectiveness ratios (cost/QALY gained) were compared to an opportunity costâbased willingnessâtoâpay threshold for Cambodia (925(IQR 376(IQR 187/QALY), cost an additional $14 485/QALY compared to the simplified model, above the willingnessâtoâpay threshold for Cambodia. This result is robust to variation in parameters.
Conclusions
The simplified model of care was cost saving compared to no treatment, emphasizing the importance of simplifying pathways of care for improving access to HCV treatment in lowâresource settings
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