703 research outputs found
Stratum Corneum Lipid Liposomes: Calcium-Induced Transformation Into Lamellar Sheets
The epidermal water barrier in mammalian stratum corneum is formed of broad lamellar sheets of lipids consisting principally of ceramides (40%), cholesterol (25%), cholesterol sulfate (10%), and free fatty acids (25%). Such lipid mixtures have been shown to form lipid bilayers in the form of small, unilamellar liposomes when sonicated at 80°C in water containing Tris buffer and 100mM NaCl. In the present study it is shown that such liposomes are slowly transformed into large unilamellar liposomes and then into broad lamellar sheets after the addition of stoichiometric amounts of calcium chloride. The presence of free fatty acids was a necessary condition for this calcium-induced fusion. These observations may provide a useful analogy for the transformation of flattened liposomes into broad lamellar sheets that occurs during transition of epidermal granular cells into corneocytes
Social evaluation at a distance – facets of stereotype content about student groups in higher distance education
In the academic domain, belonging to a negatively stereotyped group can impair performance and peer relationships. In higher distance education, stereotypes may be particularly influential as face-to-face contact is limited and non-traditional students who are at risk of being stereotyped are overrepresented. Still, research on stereotypes in higher distance education is sparse. The current research addresses this gap by investigating the Big Two of social perception (warmth, competence) and subordinate facets (friendliness, morality, assertiveness, ability, conscientiousness) in the context of higher distance education. It tests a) how well models with warmth/competence or the facets fit the data, b) whether stereotypes in higher distance education depend on the student group, and c) how the Big Two and subordinate facets predict intergroup emotions and behavioral intentions in higher distance education. An online survey with N = 626 students (74% female) of a large distance university showed that a measurement model with four facets (i.e., friendliness, morality, ability, conscientiousness) reveals adequate model fit for 12 student groups. Perceived stereotypes were positive for female students, older students, and students with children. However, migrant as well as younger students were perceived negatively. Across groups, stereotype content facets predicted intergroup emotions and behavioral intentions of facilitation or harm. Implications for the influence of negative stereotypes in higher distance education are discussed
Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites?
Leishmania parasites invade host macrophages, causing infections that are either limited to skin or spread to internal organs. In this study, 3 species causing cutaneous leishmaniasis, L. major, L. aethiopica and L. tropica, were tested for their ability to interfere with apoptosis in host macrophages in 2 different lines of human monocyte-derived macrophages (cell lines THP-1 and U937) and the results confirmed in peripheral blood mononuclear cells (PBMC). All 3 species induced early apoptosis 48 h after infection (expression of phosphatidyl serine on the outer membrane). There were significant increases in the percentage of apoptotic cells both for U937 and PBMC following infection with each of the 3 species. Early apoptotic events were confirmed by mitochondrial membrane permeabilization detection and caspase activation 48 and 72 h after infection. Moreover, the percentage of infected THP-1 and U937 macrophages increased significantly (up to 100%) following treatment with an apoptosis inducer. Since phosphatidyl serine externalization on apoptosing cells acts as a signal for engulfment by macrophages, induction of apoptosis in the parasitized cells could actively participate in spreading the infection. In summary, parasite-containing apoptotic bodies with intact membranes could be released and phagocytosed by uninfected macrophages
Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)
Using time series of Normalized Difference Vegetation Index (NDVI) and rainfall
data, we investigated historical vegetation productivity trends from 1982 to 2011
over the Bani River Basin in Mali. Statistical agreements between long-term trends
in vegetation productivty, corresponding rainfall and rate of land cover change from
Landsat time-series imagery was used to discern climate versus human-induced
vegetation cover change. Spearman correlation was used to investigate the
relationship between metrics of vegetation, rainfall trends and land cover change
categories. The results show there is a positive correlation between increases in
rainfall and some land cover classes, while some classes such as settlements were
negatively correlated with vegetation productivity trends. Croplands and Natural
Vegetation were positively correlated (r=0.89) with rainfall while settlements have a
negative correlation with NDVI time series trend (r=-057). Despite the fact that
rainfall is the major determinant of vegetation cover dynamics in the study area, it
appears that other human-induced factors such as urbanization have negatively
influenced the change in vegetation cover in the study area. The results show that a
combined analysis of NDVI, rainfall and spatially explicit land cover change
provides a comprehensive insight into the drivers of vegetation cover change in
semi-arid Africa
Assessing the inter-relationship between vegetation productivity, rainfall, population and land cover over the Bani River Basin in Mali (West Africa)
This research investigated the inter-relationship between vegetation productivity, measured using
the Normalized Difference Vegetation Index (NDVI), change in rainfall and population density in the context of
perceived greening and degradation trends over the Bani River Basin (BRB). A 30-year (1982-2011), 8-km
gridded rainfall data sets was produced by inverse distance weighted (IDW) interpolation of monthly data from
40 meteorological stations contained within the basin. Population data were retrieved from the National
Population Statistic data base for 1987, 1997, and 2009. Rainfall and NDVI time-series trends were computed
for the 30-year period and analysed. The relationship between rainfall and NDVI at pixel level, and NDVI and
population densities was analysed using a Pearson correlation. Land Use and Land Cover (LULC) conversion
rates were computed for the same period using multi-temporal 30-meter Landsat imagery; ground surveys for
selected areas within the basin were used for further cross-verification. The computed NDVI trends revealed
that, vegetation 'greening' trends are mostly associated with areas where natural vegetation is still well
represented. Concurrent with increases in rainfall over the period analysed, this finding supports the hypothesis
that re-greening observed in that area is the result of multi-decadal fluctuations in climate, rather than improved
land management
The Open Global Glacier Model (OGGM) v1.1
Despite their importance for sea-level rise, seasonal water availability, and
as a source of geohazards, mountain glaciers are one of the few remaining
subsystems of the global climate system for which no globally applicable,
open source, community-driven model exists. Here we present the Open Global
Glacier Model (OGGM), developed to provide a modular and open-source
numerical model framework for simulating past and future change of any
glacier in the world. The modeling chain comprises data downloading tools
(glacier outlines, topography, climate, validation data), a preprocessing
module, a mass-balance model, a distributed ice thickness estimation model,
and an ice-flow model. The monthly mass balance is obtained from gridded
climate data and a temperature index melt model. To our knowledge, OGGM is
the first global model to explicitly simulate glacier dynamics: the model
relies on the shallow-ice approximation to compute the depth-integrated flux
of ice along multiple connected flow lines. In this paper, we describe and
illustrate each processing step by applying the model to a selection of
glaciers before running global simulations under idealized climate forcings.
Even without an in-depth calibration, the model shows very realistic
behavior. We are able to reproduce earlier estimates of global glacier volume
by varying the ice dynamical parameters within a range of plausible values.
At the same time, the increased complexity of OGGM compared to other
prevalent global glacier models comes at a reasonable computational cost:
several dozen glaciers can be simulated on a personal computer, whereas
global simulations realized in a supercomputing environment take up to a few
hours per century. Thanks to the modular framework, modules of various
complexity can be added to the code base, which allows for new kinds of model
intercomparison studies in a controlled environment. Future developments will
add new physical processes to the model as well as automated calibration
tools. Extensions or alternative parameterizations can be easily added by the
community thanks to comprehensive documentation. OGGM spans a wide range of
applications, from ice–climate interaction studies at millennial timescales
to estimates of the contribution of glaciers to past and future sea-level
change. It has the potential to become a self-sustained community-driven
model for global and regional glacier evolution.</p
Recommended from our members
Remote sensing of vegetation fires and its contribution to a fire management information system
In the last decade, research has proven that remote sensing can provide very useful support to fire managers. This chapter provides an overview of the type of information remote sensing can provide to the fire community. It considers first fire management information needs in the context of fire management information system. An introduction to remote sensing then precedes the description of fire information obtainable from remote sensing data (such as vegetation status, active fire detection and burned areas assessment). Finally, operational examples in five African countries illustrate how the information can be used in practice
8. Remote Sensing Of Vegetation Fires And Its Contribution To A Fire Management Information System
In the last decade, research has proven that remote sensing can provide very useful support to fire managers. This chapter provides an overview of the types of information remote sensing can provide to the fire community. First, it considers fire management information needs in the context of a fire management information system. An introduction to remote sensing then precedes a description of fire information obtainable from remote sensing data (such as vegetation status, active fire detection and burned areas assessment). Finally, operational examples in five African countries illustrate the practical use of remotely sensed fire information.
As indicated in previous chapters, fire management usually comprises activities designed to control the frequency, area, intensity or impact of fire. These activities are undertaken in different institutional, economic, social, environmental and geographical contexts, as well as at different scales, from local to national. The range of fire management activities also varies considerably according to the management issues at stake, as well as the available means and capacity to act. Whatever the level, effective fire management requires reliable information upon which to base appropriate decisions and actions. Information will be required at many different stages of this fire management system. To illustrate this, we consider a typical and generic description of a fire management loop , as provided in Figure 8.1. Fire management objectives result from fire related knowledge . For example, they may relate to sound ecological reasons for prescribed burning in a particular land management context, or to frequent, uncontrolled fires threatening valuable natural or human resources. Whatever the issues, appropriate objectives require scientific knowledge (such as fire impact on ecosystems components, such as soil and vegetation), as well as up-to date monitoring information (such as vegetation status, fire locations, land use, socioeconomic context, etc.). Policies, generally at a national and governmental level, provide the official or legal long term framework (e.g. five to ten years) to undertake actions. A proper documentation of different fire issues, and their evolution, will allow their integration into appropriate policies, whether specific to fire management, or complementary to other policies in areas such as forestry, rangeland, biodiversity, land tenure, etc. Strategies are found at all levels of fire management. They provide a shorter-term framework (e.g. one to five years) to prioritise fire management activities. They involve the development of a clear set of objectives and a clear set of activities to achieve these objectives. They may also include research and training inputs required, in order to build capacity and to answer specific questions needed to improve fire management. The chosen strategy will result from a trade-off between priority fire management objectives and the available capacity to act (e.g. institutional framework, budget, staff, etc.), and will lead towards a better allocation of resources for fire management operations to achieve specific objectives. One example in achieving an objective of conserving biotic diversity may be the implementation of a patch-mosaic burning system (Brockett et al., 200 1 ) instead of a prescribed block burning system, based on an assumption that the former should better promote biodiversity in the long-term than the latter (Parr & Brockett, 1999). This strategy requires the implementation of early season fires to reduce the size of later season fires. The knowledge of population movements, new settlements or a coming El Nino season, should help focus the resources usage, as these factors might influence the proportion as well as the locations of area burned. Another strategy may be to prioritise the grading of fire lines earlier than usual based on information on high biomass accumulation. However, whatever the strategies, they need to be based on reliable information
8. Remote Sensing Of Vegetation Fires And Its Contribution To A Fire Management Information System
In the last decade, research has proven that remote sensing can provide very useful support to fire managers. This chapter provides an overview of the types of information remote sensing can provide to the fire community. First, it considers fire management information needs in the context of a fire management information system. An introduction to remote sensing then precedes a description of fire information obtainable from remote sensing data (such as vegetation status, active fire detection and burned areas assessment). Finally, operational examples in five African countries illustrate the practical use of remotely sensed fire information.
As indicated in previous chapters, fire management usually comprises activities designed to control the frequency, area, intensity or impact of fire. These activities are undertaken in different institutional, economic, social, environmental and geographical contexts, as well as at different scales, from local to national. The range of fire management activities also varies considerably according to the management issues at stake, as well as the available means and capacity to act. Whatever the level, effective fire management requires reliable information upon which to base appropriate decisions and actions. Information will be required at many different stages of this fire management system. To illustrate this, we consider a typical and generic description of a fire management loop , as provided in Figure 8.1. Fire management objectives result from fire related knowledge . For example, they may relate to sound ecological reasons for prescribed burning in a particular land management context, or to frequent, uncontrolled fires threatening valuable natural or human resources. Whatever the issues, appropriate objectives require scientific knowledge (such as fire impact on ecosystems components, such as soil and vegetation), as well as up-to date monitoring information (such as vegetation status, fire locations, land use, socioeconomic context, etc.). Policies, generally at a national and governmental level, provide the official or legal long term framework (e.g. five to ten years) to undertake actions. A proper documentation of different fire issues, and their evolution, will allow their integration into appropriate policies, whether specific to fire management, or complementary to other policies in areas such as forestry, rangeland, biodiversity, land tenure, etc. Strategies are found at all levels of fire management. They provide a shorter-term framework (e.g. one to five years) to prioritise fire management activities. They involve the development of a clear set of objectives and a clear set of activities to achieve these objectives. They may also include research and training inputs required, in order to build capacity and to answer specific questions needed to improve fire management. The chosen strategy will result from a trade-off between priority fire management objectives and the available capacity to act (e.g. institutional framework, budget, staff, etc.), and will lead towards a better allocation of resources for fire management operations to achieve specific objectives. One example in achieving an objective of conserving biotic diversity may be the implementation of a patch-mosaic burning system (Brockett et al., 200 1 ) instead of a prescribed block burning system, based on an assumption that the former should better promote biodiversity in the long-term than the latter (Parr & Brockett, 1999). This strategy requires the implementation of early season fires to reduce the size of later season fires. The knowledge of population movements, new settlements or a coming El Nino season, should help focus the resources usage, as these factors might influence the proportion as well as the locations of area burned. Another strategy may be to prioritise the grading of fire lines earlier than usual based on information on high biomass accumulation. However, whatever the strategies, they need to be based on reliable information
- …