9,019 research outputs found
Landslide Risk: Economic Valuation in the North-Eastern Zone of Medellin City
Natural disasters of a geodynamic nature can cause enormous economic and human losses. The economic costs of a landslide disaster include relocation of communities and physical repair of urban infrastructure. However, when performing a quantitative risk analysis, generally, the indirect economic consequences of such an event are not taken into account. A probabilistic approach methodology that considers several scenarios of hazard and vulnerability to measure the magnitude of the landslide and to quantify the economic costs is proposed. With this approach, it is possible to carry out a quantitative evaluation of the risk by landslides, allowing the calculation of the economic losses before a potential disaster in an objective, standardized and reproducible way, taking into account the uncertainty of the building costs in the study zone. The possibility of comparing different scenarios facilitates the urban planning process, the optimization of interventions to reduce risk to acceptable levels and an assessment of economic losses according to the magnitude of the damage. For the development and explanation of the proposed methodology, a simple case study is presented, located in north-eastern zone of the city of MedellĂn. This area has particular geomorphological characteristics, and it is also characterized by the presence of several buildings in bad structural conditions. The proposed methodology permits to obtain an estimative of the probable economic losses by earthquake-induced landslides, taking into account the uncertainty of the building costs in the study zone. The obtained estimative shows that the structural intervention of the buildings produces a reduction the order of 21 % in the total landslide risk. © Published under licence by IOP Publishing Ltd
Renormalized coordinate approach to the thermalization process
We consider a particle in the harmonic approximation coupled linearly to an
environment. modeled by an infinite set of harmonic oscillators. The system
(particle--environment) is considered in a cavity at thermal equilibrium. We
employ the recently introduced notion of renormalized coordinates to
investigate the time evolution of the particle occupation number. For
comparison we first present this study in bare coordinates. For a long ellapsed
time, in both approaches, the occupation number of the particle becomes
independent of its initial value. The value of ocupation number of the particle
is the physically expected one at the given temperature. So we have a Markovian
process, describing the particle thermalization with the environment. With
renormalized coordinates no renormalization procedure is required, leading
directly to a finite result.Comment: 16 pages, LATEX, 2 figure
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Distinctive cellular response to aluminum based adjuvants.
Aluminum-based adjuvants (ABAs) are used in human vaccines to enhance the magnitude of protective immune responses elicited against specific pathogens. One hypothesis is that stress signals released by aluminum-exposed necrotic cells play a role in modulating an immune response that contributes to the adjuvant's effectiveness. We hypothesized that aluminum adjuvant-induced necrosis would be similar irrespective of cellular origin or composition of the adjuvant. To test this hypothesis, human macrophages derived from peripheral monocytic cell line (THP-1) and cells derived from the human brain (primary astrocytes) were evaluated. Three commercially available formulations of ABAs (Alhydrogel, Imject alum, and Adju-Phos) were examined. Alum was also used as a reference. Cell viability, reactive oxygen species formation, and production of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) were quantified. Cells were exposed to different concentrations (10-100 μg/mL) of the adjuvants for 24 h or 72 h. The two FDA approved adjuvants (Alhydrogel and Adju-Phos) decreased cell viability in both cell types. At the 72 h time point, the decrease in viability was accompanied with increased ROS formation. The size of the aluminum agglomerates was not relatable to the changes observed. After exposure to ABAs, astrocytes and macrophages presented a distinct profile of cytokine secretion which may relate to the function and unique characteristics of each cell type. These variations indicate that aluminum adjuvants may have differing capability of activating cells of different origin and thus their utility in specific vaccine design should be carefully assessed for optimum efficacy
The role of industry, occupation, and location specific knowledge in the survival of new firms
How do regions acquire the knowledge they need to diversify their economic
activities? How does the migration of workers among firms and industries
contribute to the diffusion of that knowledge? Here we measure the industry,
occupation, and location-specific knowledge carried by workers from one
establishment to the next using a dataset summarizing the individual work
history for an entire country. We study pioneer firms--firms operating in an
industry that was not present in a region--because the success of pioneers is
the basic unit of regional economic diversification. We find that the growth
and survival of pioneers increase significantly when their first hires are
workers with experience in a related industry, and with work experience in the
same location, but not with past experience in a related occupation. We compare
these results with new firms that are not pioneers and find that
industry-specific knowledge is significantly more important for pioneer than
non-pioneer firms. To address endogeneity we use Bartik instruments, which
leverage national fluctuations in the demand for an activity as shocks for
local labor supply. The instrumental variable estimates support the finding
that industry-related knowledge is a predictor of the survival and growth of
pioneer firms. These findings expand our understanding of the micro-mechanisms
underlying regional economic diversification events
Slip avalanches in a fiber bundle model
We study slip avalanches in disordered materials under an increasing external
load in the framework of a fiber bundle model. Over-stressed fibers of the
model do not break, instead they relax in a stick-slip event which may trigger
an entire slip avalanche. Slip avalanches are characterized by the number
slipping fibers, by the slip length, and by the load increment, which triggers
the avalanche. Our calculations revealed that all three quantities are
characterized by power law distributions with universal exponents. We show by
analytical calculations and computer simulations that varying the amount of
disorder of slip thresholds and the number of allowed slips of fibers, the
system exhibits a disorder induced phase transition from a phase where only
small avalanches are formed to another one where a macroscopic slip appears.Comment: 6 pages, 6 figure
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