4,437 research outputs found
Effects of regional differences and demography in modelling foot-and-mouth disease in cattle at the national scale
Foot-and-mouth disease (FMD) is a fast-spreading viral infection that can produce large and costly outbreaks in livestock populations. Transmission occurs at multiple spatial scales, as can the actions used to control outbreaks. The US cattle industry is spatially expansive, with heterogeneous distributions of animals and infrastructure. We have developed a model that incorporates the effects of scale for both disease transmission and control actions, applied here in simulating FMD outbreaks in US cattle. We simulated infection initiating in each of the 3049 counties in the contiguous US, 100 times per county. When initial infection was located in specific regions, large outbreaks were more likely to occur, driven by infrastructure and other demographic attributes such as premises clustering and number of cattle on premises. Sensitivity analyses suggest these attributes had more impact on outbreak metrics than the ranges of estimated disease parameter values. Additionally, although shipping accounted for a small percentage of overall transmission, areas receiving the most animal shipments tended to have other attributes that increase the probability of large outbreaks. The importance of including spatial and demographic heterogeneity in modelling outbreak trajectories and control actions is illustrated by specific regions consistently producing larger outbreaks than others
Cross-reactive neutralizing antibody response to enterovirus 71 infection in Taiwanese young children
The application of ultrasonic NDT techniques in tribology
The use of ultrasonic reflection is emerging as a technique for studying tribological contacts. Ultrasonic waves can be transmitted non-destructively through machine components and their behaviour at an interface describes the characteristics of that contact. This paper is a review of the current state of understanding of the mechanisms of ultrasonic reflection at interfaces, and how this has been used to investigate the processes of dry rough surface contact and lubricated contact. The review extends to cover how ultrasound has been used to study the tribological function of certain engineering machine elements
LMP1 of Epstein-Barr virus induces proliferation of primary mouse embryonic fibroblasts and cooperatively transforms the cells with a p16-insensitive CDK4 oncogene
The latent membrane protein LMP1 of Epstein-Barr virus (EBV) is often present in EBV-associated malignancies including nasopharyngeal carcinoma and Hodgkin's lymphoma. Previous work demonstrates that the LMP1 gene of EBV is sufficient to transform certain established rodent fibroblast cell lines and to induce the tumorigenicity of some human epithelial cell lines. In addition, LMP1 plays pleiotropic roles in cell growth arrest, differentiation, and apoptosis, depending on the background of the target cells. To examine the roles of LMP1 in cell proliferation and growth regulation in primary culture cells, we constructed a recombinant retrovirus containing an LMP1 gene. With this retrovirus, LMP1 was shown to stimulate the proliferation of primary mouse embryonic fibroblasts (MEF cells). It has a mitogenic activity for MEF cells, as demonstrated by an immediate induction of cell doubling time, In addition, it significantly extends the passage number of MEF cells to more than 30 after retroviral infection, compared with less than 5 for uninfected MEF cells. Furthermore, LMP1 cooperates with a pl6-insensitive CDK4(R24C) oncogene in transforming MEF cells. Our results provide the first evidence of the abilities of the LMP1 gene, acting alone, to effectively induce the proliferation of primary MEF cells and of its cooperativity with another cellular oncogene in transforming primary cells
On the stability of high-speed milling with spindle speed variation
Spindle speed variation is a well-known technique to suppress regenerative machine tool vibrations, but it is usually considered to be effective only for low spindle speeds. In this paper, the effect of spindle speed variation is analyzed in the high-speed domain for spindle speeds corresponding to the first flip (period doubling) and to the first Hopf lobes. The optimal amplitudes and frequencies of the speed modulations are computed using the semidiscre- tization method. It is shown that period doubling chatter can effectively be suppressed by spindle speed variation, although, the technique is not effective for the quasiperiodic chatter above the Hopf lobe. The results are verified by cutting tests. Some special cases are also discussed where the practical behavior of the system differs from the predicted one in some ways. For these cases, it is pointed out that the concept of stability is understood on the scale of the principal period of the system—that is, the speed modulation period for variable spindle speed machining and the tooth passing period for constant spindle speed machining
Use of new radiochromic devices for peripheral dose measurement: potential in-vivo dosimetry application
The authors have studied the feasibility of using three new high-sensitivity radiochromic devices in measuring the doses to peripheral points outside the primary megavoltage photon beams. The three devices were GAFCHROMIC® EBT film, prototype Low Dose (LD) Film, and prototype LD Card. The authors performed point dosimetry using these three devices in water-equivalent solid phantoms at x = 3,5,8,10, and 15 cm from the edge of 6 MV and 15 MV photon beams of 10x10 cm2, and at depths of 0, 0.5 cm, and depth of maximum dose. A full sheet of EBT film was exposed with 5000 MU. The prototype LD film pieces were 1.5x2 cm2 in size. Some LD films were provided in the form of a card in 1.8x5 cm2 holding an active film in 1.8x2 cm2. These are referred to as “LD dosimeter cards”. The small LD films and cards were exposed with 500 MU. For each scanned film, a 6 mm circular area centered at the measurement point was sampled and the mean pixel value was obtained. The calibration curves were established from the calibration data for each combination of film/cards and densitometer/scanner. The doses at the peripheral points determined from the films were compared with those obtained using ion chamber at respective locations in a water phantom and general agreements were found. It is feasible to accurately measure peripheral doses of megavoltage photon beams using the new high-sensitivity radiochromic devices. This near real-time and inexpensive method can be applied in a clinical setting for dose measurements to critical organs and sensitive patient implant devices
Present status and future prospects for a Higgs boson discovery at the Tevatron and LHC
Discovering the Higgs boson is one of the primary goals of both the Tevatron
and the Large Hadron Collider (LHC). The present status of the Higgs search is
reviewed and future prospects for discovery at the Tevatron and LHC are
considered. This talk focuses primarily on the Higgs boson of the Standard
Model and its minimal supersymmetric extension. Theoretical expectations for
the Higgs boson and its phenomenological consequences are reviewed.Comment: 13 pages, 9 figures, 2 tables, jpconf documentclass file, invited
talk at PASCOS 2010, the 16th International Symposium on Particles, Strings
and Cosmology, Valencia, Spain, 19--23 July 201
Boojums and the Shapes of Domains in Monolayer Films
Domains in Langmuir monolayers support a texture that is the two-dimensional
version of the feature known as a boojum. Such a texture has a quantifiable
effect on the shape of the domain with which it is associated. The most
noticeable consequence is a cusp-like feature on the domain boundary. We report
the results of an experimental and theoretical investigation of the shape of a
domain in a Langmuir monolayer. A further aspect of the investigation is the
study of the shape of a ``bubble'' of gas-like phase in such a monolayer. This
structure supports a texture having the form of an inverse boojum. The
distortion of a bubble resulting from this texture is also studied. The
correspondence between theory and experiment, while not perfect, indicates that
a qualitative understanding of the relationship between textures and domain
shapes has been achieved.Comment: replaced with published version, 10 pages, 13 figures include
Energetics and atomic mechanisms of dislocation nucleation in strained epitaxial layers
We study numerically the energetics and atomic mechanisms of misfit
dislocation nucleation and stress relaxation in a two-dimensional atomistic
model of strained epitaxial layers on a substrate with lattice misfit.
Relaxation processes from coherent to incoherent states for different
transition paths are studied using interatomic potentials of Lennard-Jones type
and a systematic saddle point and transition path search method. The method is
based on a combination of repulsive potential minimization and the Nudged
Elastic Band method. For a final state with a single misfit dislocation, the
minimum energy path and the corresponding activation barrier are obtained for
different misfits and interatomic potentials. We find that the energy barrier
decreases strongly with misfit. In contrast to continuous elastic theory, a
strong tensile-compressive asymmetry is observed. This asymmetry can be
understood as manifestation of asymmetry between repulsive and attractive
branches of pair potential and it is found to depend sensitively on the form of
the potential.Comment: 11 pages, 9 figures, to appear in Phys. Rev.
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