1,291 research outputs found
Yield-maturity relationships in spring-planted crops for the northern Canadian prairies
Non-Peer Reviewe
Intra-Class Testing of Abstract Class Features
One of the characteristics of the increasingly widespread
use of object-oriented libraries and the resulting intensive
use of inheritance is the proliferation of dependencies on
abstract classes. Such classes defer the implementation of
some features, and are typically used as a specification or
design tool. However, since their features are not fully implemented,abstract classes cannot be instantiated, and thus pose challenges for execution-based testing strategies.
This paper presents a structured approach that supports
the testing of features in abstract classes. Core to the approach is a series of static analysis steps that build a comprehensive view of the inter-class dependencies in the system under test. We then leveraged this information to define a test order for the methods in an abstract class that minimizes the number of stubs required during testing, and clearly identifies the required functionality of these stubs.
Our approach is based on a comprehensive taxonomy of
object-oriented classes that provides a framework for our
analysis. First we describe the algorithms to calculate the
inter-class dependencies and the test-order that minimizes
stub creation. Then we give an overview of our tool, AbstractTestJ that implements our approach by generating a
test order for the methods in an abstract Java class. Finally, we harness this tool to provide an analysis of 12 substantial Java applications that demonstrates both the feasibility of our approach and the importance of this technique
What makes medical students better listeners?
Diagnosing heart conditions by auscultation is an important clinical skill commonly learnt by medical students. Clinical proficiency for this skill is in decline [1], and new teaching methods are needed. Successful discrimination of heartbeat sounds is believed to benefit mainly from acoustical training [2]. From recent studies of auditory training [3,4] we hypothesized that semantic representations outside the auditory cortex contribute to diagnostic accuracy in cardiac auscultation. To test this hypothesis, we analysed auditory evoked potentials (AEPs) which were recorded from medical students while they diagnosed quadruplets of heartbeat cycles. The comparison of trials with correct (Hits) versus incorrect diagnosis (Misses) revealed a significant difference in brain activity at 280-310 ms after the onset of the second cycle within the left middle frontal gyrus (MFG) and the right prefrontal cortex. This timing and locus suggest that semantic rather than acoustic representations contribute critically to auscultation skills. Thus, teaching auscultation should emphasize the link between the heartbeat sound and its meaning. Beyond cardiac auscultation, this issue is of interest for all fields where subtle but complex perceptual differences identify items in a well-known semantic context
Singular Casimir Elements of the Euler Equation and Equilibrium Points
The problem of the nonequivalence of the sets of equilibrium points and
energy-Casimir extremal points, which occurs in the noncanonical Hamiltonian
formulation of equations describing ideal fluid and plasma dynamics, is
addressed in the context of the Euler equation for an incompressible inviscid
fluid. The problem is traced to a Casimir deficit, where Casimir elements
constitute the center of the Lie-Poisson algebra underlying the Hamiltonian
formulation, and this leads to a study of the symplectic operator defining the
Poisson bracket. The kernel of the symplectic operator, for this typical
example of an infinite-dimensional Hamiltonian system for media in terms of
Eulerian variables, is analyzed. For two-dimensional flows, a rigorously
solvable system is formulated. The nonlinearity of the Euler equation makes the
symplectic operator inhomogeneous on phase space (the function space of the
state variable), and it is seen that this creates a singularity where the
nullity of the symplectic operator (the "dimension" of the center) changes.
Singular Casimir elements stemming from this singularity are unearthed using a
generalization of the functional derivative that occurs in the Poisson bracket
Environmental requirements for three sea pen species: relevance to distribution and conservation
The aim is to determine the environmental requirements, estimate the extent of suitable habitat for three sea pen species, and assess the implications for marine protected areas (MPAs). The sea pen Funiculina quadrangularis and the habitat associated with two further sea pen species,
Virgularia mirabilis and Pennatula phosphorea, are of key conservation importance and are recommended for protection within MPAs. This
study models their potential distributions using the MAXimum ENTropy algorithm and assesses these in relation to five possible marine protected
areas (pMPAs) proposed for Scottish waters. Metrics relevant to assessing the efficacy of MPAs are also presented. Four environmental variables of
prime importance for predicting the presence of all three species of sea pen were identified: mud, minimum salinity, depth, and gravel. The habitat
suitability index increased with mud content. The modelled distribution of F. quadrangularis indicated a deeper distribution than V. mirabilis or
P. phosphorea and was not present in sediment with gravel content above 30%. Pennatula phosphorea had the smallest area of suitable habitat, while
V. mirabilis had the largest. The percentage predicted suitable area for each species that was encompassed by the five pMPAs ranged from 11% for
F. quadrangularis to 15% for P. phosphorea. Some of the largest areas predicted as suitable for F. quadrangularis lay outside the pMPAs. The model
results indicated differences in the environmental requirements of the three species of sea pen that can be linked to the autecology of each species.
Patch sizes, calculated from a binary output of the model, were used to estimate the degree of habitat fragmentation, thereby giving a partial
assessment of the adequacy criterion for these pMPAs. The results suggest that potential MPAs within the study area cover sizeable areas of
potential sea pen habitat. However, further areas suitable for F. quadrangularis could be considered
Magnetic fluctuations and spin freezing in nonsuperconducting LiFeAs derivatives
We present detailed magnetometry and muon-spin rotation data on polycrystalline samples of overdoped, nonsuperconducting LiFe1−xNixAs (x = 0.1,0.2) and Li1−yFe1+yAs (0 y 0.04) as well as superconducting LiFeAs.While LiFe1−xNixAs exhibits weak antiferromagnetic fluctuations down to 1.5 K,Li1−yFe1+yAs samples, which have a much smaller deviation from the 1 : 1 : 1 stoichiometry, show a crossover from ferromagnetic to antiferromagnetic fluctuations on cooling and a freezing of dynamically fluctuating moments at low temperatures. We do not find any signatures of time-reversal symmetry breaking in stoichiometric LiFeAs that would support recent predictions of triplet pairing
Self-Seeding of a Gain-Switched Integrated Dual-Laser Source for the Generation of Highly Wavelength-Tunable Picosecond Optical Pulses
Homocysteine and brain atrophy on MRI of non-demented elderly
Patients with Alzheimer's disease have higher plasma homocysteine levels
than controls, but it is uncertain whether higher plasma homocysteine
levels are involved in the early pathogenesis of the disease. Hippocampal,
amygdalar and global brain atrophy on brain MRI have been proposed as
early markers of Alzheimer's disease. In the Rotterdam Scan Study, a
population-based study of age-related brain changes in 1077 non-demented
people aged 60-90 years, we investigated the association between plasma
homocysteine levels and severity of hippocampal, amygdalar and global
brain atrophy on MRI. We used axial T(1)-weighted MRIs to visualize global
cortical brain atrophy (measured semi-quantitatively; range 0-15) and a 3D
HASTE (half-Fourier acquisition single-shot turbo spin echo) sequence in
511 participants to measure hippocampal and amygdalar volumes. We had
non-fasting plasma homocysteine levels in 1031 of the participants and in
505 of the participants with hippocampal and amygdalar volumes.
Individuals with higher plasma homocysteine levels had, on average, more
cortical atrophy [0.23 units (95% CI 0.07-0.38 units) per standard
deviation increase in plasma homocysteine levels] and more hippocampal
atrophy [difference in left hippocampal volume -0.05 ml (95% CI -0.09 to
-0.01) and in right hippocampal volume -0.03 ml (95% CI -0.07 to 0.01) per
standard deviation increase in plasma homocysteine levels]. No association
was observed between plasma homocysteine levels and amygdalar atrophy.
These results support the hypothesis that higher plasma homocysteine
levels are associated with more atrophy of the hippocampus and cortical
regions in elderly at risk of Alzheimer's disease
Electromigration-Induced Flow of Islands and Voids on the Cu(001) Surface
Electromigration-induced flow of islands and voids on the Cu(001) surface is
studied at the atomic scale. The basic drift mechanisms are identified using a
complete set of energy barriers for adatom hopping on the Cu(001) surface,
combined with kinetic Monte Carlo simulations. The energy barriers are
calculated by the embedded atom method, and parameterized using a simple model.
The dependence of the flow on the temperature, the size of the clusters, and
the strength of the applied field is obtained. For both islands and voids it is
found that edge diffusion is the dominant mass-transport mechanism. The rate
limiting steps are identified. For both islands and voids they involve
detachment of atoms from corners into the adjacent edge. The energy barriers
for these moves are found to be in good agreement with the activation energy
for island/void drift obtained from Arrhenius analysis of the simulation
results. The relevance of the results to other FCC(001) metal surfaces and
their experimental implications are discussed.Comment: 9 pages, 13 ps figure
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