16,788 research outputs found
Evaluating the Long-run Impacts of the 9/11 Terrorist Attacks on US Domestic Airline Travel
Although the US airline industry began 2001 with 24 consecutive profitable quarters, including net profits in 2000 totaling $7.9 billion, the impact of the 9/11 event on the industry was substantial. Whereas the recession that began in early 2001 signaled the end of profitability, the 9/11 terrorist attacks pushed the industry into financial crisis after air travel dropped 20% over the September–December 2001 period compared to the same period in 2000. Given the decline in domestic air travel, an important question is whether the detrimental impact of the attacks was temporary or permanent. That is, did airline travel return to the trend that existed prior to the terrorist attacks? There are theoretical reasons to the believe that it would not. Economists have long viewed travel-mode choices as the outcome of a comparison of opportunity costs and benefits. Thus, anything that permanently raises the opportunity cost of travel, holding benefits constant, should reduce the level of travel volume. To determine whether air travel was permanently reduced, we use econometric and time-series forecasting models to generate a counter-factual forecast of air travel volume in the absence of the terrorist attacks. These dynamic forecasts are compared to actual air travel levels to determine the impact of the terrorist attacks. The findings suggest that domestic air travel did not return to the levels that would have existed in the absence of the attack
Towards a Java Subtyping Operad
The subtyping relation in Java exhibits self-similarity. The self-similarity
in Java subtyping is interesting and intricate due to the existence of wildcard
types and, accordingly, the existence of three subtyping rules for generic
types: covariant subtyping, contravariant subtyping and invariant subtyping.
Supporting bounded type variables also adds to the complexity of the subtyping
relation in Java and in other generic nominally-typed OO languages such as C#
and Scala. In this paper we explore defining an operad to model the
construction of the subtyping relation in Java and in similar generic
nominally-typed OO programming languages. Operads, from category theory, are
frequently used to model self-similar phenomena. The Java subtyping operad, we
hope, will shed more light on understanding the type systems of generic
nominally-typed OO languages.Comment: 13 page
Precision cosmology defeats void models for acceleration
The suggestion that we occupy a privileged position near the centre of a
large, nonlinear, and nearly spherical void has recently attracted much
attention as an alternative to dark energy. Putting aside the philosophical
problems with this scenario, we perform the most complete and up-to-date
comparison with cosmological data. We use supernovae and the full cosmic
microwave background spectrum as the basis of our analysis. We also include
constraints from radial baryonic acoustic oscillations, the local Hubble rate,
age, big bang nucleosynthesis, the Compton y-distortion, and for the first time
include the local amplitude of matter fluctuations, \sigma_8. These all paint a
consistent picture in which voids are in severe tension with the data. In
particular, void models predict a very low local Hubble rate, suffer from an
"old age problem", and predict much less local structure than is observed.Comment: 22 pages, 12 figures; v2 adds models in closed backgrounds;
conclusions strengthened; version accepted to Phys. Rev.
Diversity-induced resonance in a system of globally coupled linear oscillators
The purpose of this paper to analyze in some detail the arguably simplest
case of diversity-induced reseonance: that of a system of globally-coupled
linear oscillators subjected to a periodic forcing. Diversity appears as the
parameters characterizing each oscillator, namely its mass, internal frequency
and damping coefficient are drawn from a probability distribution. The main
ingredients for the diversity-induced-resonance phenomenon are present in this
system as the oscillators display a variability in the individual responses but
are induced, by the coupling, to synchronize their responses. A steady state
solution for this model is obtained. We also determine the conditions under
which it is possible to find a resonance effect.Comment: Reported at the XI International Workshop "Instabilities and
Nonequilibrium Structures" Vina del Mar (Chile
Dynamic plantar loading index detects altered foot function in individuals with rheumatoid arthritis but not changes due to orthotic use
Background Altered foot function is common in individuals with rheumatoid arthritis. Plantar pressure distributions during gait are regularly assessed in this patient group; however, the association between frequently reported magnitude-based pressure variables and clinical outcomes has not been clearly established. Recently, a novel approach to the analysis of plantar pressure distributions throughout stance phase, the dynamic plantar loading index, has been proposed. This study aimed to assess the utility of this index for measuring foot function in individuals with rheumatoid arthritis.Methods Barefoot plantar pressures during gait were measured in 63 patients with rheumatoid arthritis and 51 matched controls. Additionally, 15 individuals with rheumatoid arthritis had in-shoe plantar pressures measured whilst walking in standardized footwear for two conditions: shoes-only; and shoes with prescribed custom foot orthoses. The dynamic plantar loading index was determined for all participants and conditions. Patient and control groups were compared for significant differences as were the shod and orthosis conditions.Findings The patient group was found to have a mean index of 0.19, significantly lower than the control group's index of 0.32 (p > 0.001, 95% CI [0.054, 0.197]). No significant differences were found between the shoe-only and shoe plus orthosis conditions. The loading index was found to correlate with clinical measures of structural deformity.Interpretation The dynamic plantar loading index may be a useful tool for researchers and clinicians looking to objectively assess dynamic foot function in patients with rheumatoid arthritis; however, it may be unresponsive to changes caused by orthotic interventions in this patient group.</p
Deep proteogenomics; high throughput gene validation by multidimensional liquid chromatography and mass spectrometry of proteins from the fungal wheat pathogen Stagonospora nodorum
BACKGROUND: Stagonospora nodorum, a fungal ascomycete in the class dothideomycetes, is a
damaging pathogen of wheat. It is a model for necrotrophic fungi that cause necrotic symptoms via
the interaction of multiple effector proteins with cultivar-specific receptors. A draft genome
sequence and annotation was published in 2007. A second-pass gene prediction using a training set
of 795 fully EST-supported genes predicted a total of 10762 version 2 nuclear-encoded genes, with
an additional 5354 less reliable version 1 genes also retained.
RESULTS: In this study, we subjected soluble mycelial proteins to proteolysis followed by 2D LC
MALDI-MS/MS. Comparison of the detected peptides with the gene models validated 2134 genes.
62% of these genes (1324) were not supported by prior EST evidence. Of the 2134 validated genes,
all but 188 were version 2 annotations. Statistical analysis of the validated gene models revealed a
preponderance of cytoplasmic and nuclear localised proteins, and proteins with intracellularassociated
GO terms. These statistical associations are consistent with the source of the peptides
used in the study. Comparison with a 6-frame translation of the S. nodorum genome assembly
confirmed 905 existing gene annotations (including 119 not previously confirmed) and provided
evidence supporting 144 genes with coding exon frameshift modifications, 604 genes with
extensions of coding exons into annotated introns or untranslated regions (UTRs), 3 new gene
annotations which were supported by tblastn to NR, and 44 potential new genes residing within
un-assembled regions of the genome.
CONCLUSION: We conclude that 2D LC MALDI-MS/MS is a powerful, rapid and economical tool to
aid in the annotation of fungal genomic assemblies
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