23,286 research outputs found
Monitoring and control in scenario-based requirements analysis
Scenarios are an effective means for eliciting, validating and documenting requirements. At the requirements level, scenarios describe sequences of interactions between the software-to-be and agents in the environment. Interactions correspond to the occurrence of an event that is controlled by one agent and monitored by another.This paper presents a technique to analyse requirements-level scenarios for unforeseen, potentially harmful, consequences. Our aim is to perform analysis early in system development, where it is highly cost-effective. The approach recognises the importance of monitoring and control issues and extends existing work on implied scenarios accordingly. These so-called input-output implied scenarios expose problematic behaviours in scenario descriptions that cannot be detected using standard implied scenarios. Validation of these implied scenarios supports requirements elaboration. We demonstrate the relevance of input-output implied scenarios using a number of examples
Expression of PEG11 and PEG11AS transcripts in normal and callipyge sheep
BACKGROUND: The callipyge mutation is located within an imprinted gene cluster on ovine chromosome 18. The callipyge trait exhibits polar overdominant inheritance due to the fact that only heterozygotes inheriting a mutant paternal allele (paternal heterozygotes) have a phenotype of muscle hypertrophy, reduced fat and a more compact skeleton. The mutation is a single A to G transition in an intergenic region that results in the increased expression of several genes within the imprinted cluster without changing their parent-of-origin allele-specific expression. RESULTS: There was a significant effect of genotype (p < 0.0001) on the transcript abundance of DLK1, PEG11, and MEG8 in the muscles of lambs with the callipyge allele. DLK1 and PEG11 transcript levels were elevated in the hypertrophied muscles of paternal heterozygous animals relative to animals of the other three genotypes. The PEG11 locus produces a single 6.5 kb transcript and two smaller antisense strand transcripts, referred to as PEG11AS, in skeletal muscle. PEG11AS transcripts were detectable over a 5.5 kb region beginning 1.2 kb upstream of the PEG11 start codon and spanning the entire open reading frame. Analysis of PEG11 expression by quantitative PCR shows a 200-fold induction in the hypertrophied muscles of paternal heterozygous animals and a 13-fold induction in homozygous callipyge animals. PEG11 transcripts were 14-fold more abundant than PEG11AS transcripts in the gluteus medius of paternal heterozygous animals. PEG11AS transcripts were expressed at higher levels than PEG11 transcripts in the gluteus medius of animals of the other three genotypes. CONCLUSIONS: The effect of the callipyge mutation has been to alter the expression of DLK1, GTL2, PEG11 and MEG8 in the hypertrophied skeletal muscles. Transcript abundance of DLK1 and PEG11 was highest in paternal heterozygous animals and exhibited polar overdominant gene expression patterns; therefore, both genes are candidates for causing skeletal muscle hypertrophy. There was unique relationship of PEG11 and PEG11AS transcript abundance in the paternal heterozygous animals that suggests a RNA interference mechanism may have a role in PEG11 gene regulation and polar overdominance in callipyge sheep
BMBF-Verbundprojekt "Informationsmanagement der Zukunft in regionalen Lebensmittelketten" (RegioFood_Plus): Aufbau und Ziele
One obstacle for the access of micro sized food enterprises to trading chains is the lack of IT based real-time specifications for produce, and to-date availability of information about management. To resolve this, a research project has established to develop an user-optimised, cloud-based enterprice resource planning (ERP) system that is tailored to suit the needs of such small enterprises. New functions such as reporting systems for food management and sustainability certification reports will be integrated. As a first result, an analysis showed that approx. 11 per cent of process based criteria of IFS and BRC certification can be mapped with to-date ERP systems, accentuating the need for this development
Null Branes in Curved Backgrounds
We consider null bosonic p-branes in curved space-times. Some exact solutions
of the classical equations of motion and of the constraints for the null
membrane in general stationary, axially symmetrical, four dimensional, gravity
background are found.Comment: 19 pages, LaTeX, no figures. Extended version. To appear in Phys.
Rev.
The Formation of the Double Pulsar PSR J0737-3039A/B
Recent timing observations of the double pulsar J0737-3039A/B have shown that
its transverse velocity is extremely low, only 10 km/s, and nearly in the Plane
of the Galaxy. With this new information, we rigorously re-examine the history
and formation of this system, determining estimates of the pre-supernova
companion mass, supernova kick and misalignment angle between the pre- and
post-supernova orbital planes. We find that the progenitor to the recently
formed `B' pulsar was probably less than 2 MSun, lending credence to
suggestions that this object may not have formed in a normal supernova
involving the collapse of an iron core. At the same time, the supernova kick
was likely non-zero. A comparison to the history of the double-neutron-star
binary B1534+12 suggests a range of possible parameters for the progenitors of
these systems, which should be taken into account in future binary population
syntheses and in predictions of the rate and spatial distribution of short
gamma-ray burst events.Comment: To appear in MNRAS Letters. Title typo fix only; no change to pape
Limitations on the smooth confinement of an unstretchable manifold
We prove that an m-dimensional unit ball D^m in the Euclidean space {\mathbb
R}^m cannot be isometrically embedded into a higher-dimensional Euclidean ball
B_r^d \subset {\mathbb R}^d of radius r < 1/2 unless one of two conditions is
met -- (1)The embedding manifold has dimension d >= 2m. (2) The embedding is
not smooth. The proof uses differential geometry to show that if d<2m and the
embedding is smooth and isometric, we can construct a line from the center of
D^m to the boundary that is geodesic in both D^m and in the embedding manifold
{\mathbb R}^d. Since such a line has length 1, the diameter of the embedding
ball must exceed 1.Comment: 20 Pages, 3 Figure
An explanation of the Newman-Janis Algorithm
After the original discovery of the Kerr metric, Newman and Janis showed that
this solution could be ``derived'' by making an elementary complex
transformation to the Schwarzschild solution. The same method was then used to
obtain a new stationary axisymmetric solution to Einstein's field equations now
known as the Kerr-newman metric, representing a rotating massive charged black
hole. However no clear reason has ever been given as to why the Newman-Janis
algorithm works, many physicist considering it to be an ad hoc procedure or
``fluke'' and not worthy of further investigation. Contrary to this belief this
paper shows why the Newman-Janis algorithm is successful in obtaining the
Kerr-Newman metric by removing some of the ambiguities present in the original
derivation. Finally we show that the only perfect fluid generated by the
Newman-Janis algorithm is the (vacuum) Kerr metric and that the only Petrov
typed D solution to the Einstein-Maxwell equations is the Kerr-Newman metric.Comment: 14 pages, no figures, submitted to Class. Quantum Gra
Mesoscopic Hall effect driven by chiral spin order
A Hall effect due to spin chirality in mesoscopic systems is predicted. We
consider a 4-terminal Hall system including local spins with geometry of a
vortex domain wall, where strong spin chirality appears near the center of
vortex. The Fermi energy of the conduction electrons is assumed to be
comparable to the exchange coupling energy where the adiabatic approximation
ceases to be valid. Our results show a Hall effect where a voltage drop and a
spin current arise in the transverse direction. The similarity between this
Hall effect and the conventional spin Hall effect in systems with spin-orbit
interaction is pointed out.Comment: 4 pages, 4 figure
Scaling of the buckling transition of ridges in thin sheets
When a thin elastic sheet crumples, the elastic energy condenses into a
network of folding lines and point vertices. These folds and vertices have
elastic energy densities much greater than the surrounding areas, and most of
the work required to crumple the sheet is consumed in breaking the folding
lines or ``ridges''. To understand crumpling it is then necessary to understand
the strength of ridges. In this work, we consider the buckling of a single
ridge under the action of inward forcing applied at its ends. We demonstrate a
simple scaling relation for the response of the ridge to the force prior to
buckling. We also show that the buckling instability depends only on the ratio
of strain along the ridge to curvature across it. Numerically, we find for a
wide range of boundary conditions that ridges buckle when our forcing has
increased their elastic energy by 20% over their resting state value. We also
observe a correlation between neighbor interactions and the location of initial
buckling. Analytic arguments and numerical simulations are employed to prove
these results. Implications for the strength of ridges as structural elements
are discussed.Comment: 42 pages, latex, doctoral dissertation, to be submitted to Phys Rev
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