2,601 research outputs found
Deformation modes and geometries in the EPICA-DML ice core, Antarctica
Combination of physical-properties methods (crystal-orientation-fabrics, grain-elongation-data, line-scan stratigraphy-documentation) reveal evidences for five deformation geometry regimes:1. Random c-axes distributions and crystal elongation directions (~2020 m depth). Here bed-parallel simple shear deforms the ice causing folding and inclination of stratigraphic layers.5. A last change of geometries is observed at ~2370 m depth, with a locally very restricted (~10 m) backslide to girdle fabric, isoclinal z-folding and borehole closure. Below that an inclined single maximum fabric reoccurs.Simple shear can easily produce the observed small-scale folding of layers which however may belong to disturbances on a larger scale with possible overturning and thus age reversal of layers. Below ~2020 m the EDML climate record has to be interpreted with great care
Immunologists getting nervous: neuropeptides, dendritic cells and T cell activation
It is increasingly recognised that the immune and nervous systems are closely integrated to optimise defence systems within the lung. In this commentary, the contribution of various neuropeptides such as substance P, calcitonin gene-related peptide, vasoactive intestinal peptide and somatostatin to the regulation of T cell activation is discussed. These neuropeptides are released not only from nerve endings but also from inflammatory immune cells such as monocytes, dendritic cells, eosinophils and mast cells. On release they can exert both direct stimulatory and inhibitory effects on T cell activation and also indirect effects through their influence on the recruitment and activation of professional antigen-presenting dendritic cells. Neuropeptides should therefore be included in the conceptual framework of the immune regulation of T cell function by dendritic cells
Casimir effect with rough metallic mirrors
We calculate the second order roughness correction to the Casimir energy for
two parallel metallic mirrors. Our results may also be applied to the
plane-sphere geometry used in most experiments. The metallic mirrors are
described by the plasma model, with arbitrary values for the plasma wavelength,
the mirror separation and the roughness correlation length, with the roughness
amplitude remaining the smallest length scale for perturbation theory to hold.
From the analysis of the intracavity field fluctuations, we obtain the
Casimir energy correction in terms of generalized reflection operators, which
account for diffraction and polarization coupling in the scattering by the
rough surfaces. We present simple analytical expressions for several limiting
cases, as well as numerical results that allow for a reliable calculation of
the roughness correction in real experiments. The correction is larger than the
result of the Proximity Force Approximation, which is obtained from our theory
as a limiting case (very smooth surfaces).Comment: 16 page
Innate Immune Cells to the Help
A study by Halim and Steer (2014) in this issue of Immunity shows that innate lymphoid cells type 2 (ILC2s) are crucial for inducing adaptive T helper 2 immunity by providing interleukin-13. Another study by van Dyken et al. (2014) shows that ILC2s control eosinophilia and alternative activation of macrophages
A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus
The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. In some regions, the observed reduction in glacier area is comparable to those in the European Alps and the extent of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no continuous field measurements are available. In this study, regional differences of the conditions for glacier melt with a special focus on debris covered glacier tongues in the well-studied Adyl-su basin on the northern slope of the Caucasus Mountains (Russia) is compared with the Zopkhito basin which has similar characteristics but is located on the southern slope in Georgia. The paper focuses on the effect of supra-glacial debris cover on glacier summer melt. There are systematic differences in the distribution and increase of the debris cover on the glaciers of the two basins. In the Adyl-su basin an extensive debris cover on the glacier tongues is common, however, only those glacier tongues that are positioned at the lowest elevations in the Zopkhito basin show a considerable extent of supra-glacial debris. The observed increase in debris cover is considerably stronger in the north. Field experiments show that thermal resistance of the debris cover in both basins is somewhat higher than in other glaciated regions of the world, but there is also a significant difference between the two regions. A simple ablation model accounting for the effect of debris cover on ice melt shows that melt rates are considerably higher in the northern basin despite a wider debris distribution. This difference between the two regions can be attributed to different meteorological conditions which are characterised by more frequent cloud cover and precipitation in the south. Furthermore ablation is strongly influenced by the occurrence of supra-glacial debris cover in both basins, reducing the total amount of melt on the studied glaciers by about 25 %. This effect mitigates glacier retreat in the lower sectors of the ablation zones considerably. The sensitivity to moderate changes in the debris cover, however, is rather small which implies only gradual changes of the melt regime due to debris cover dynamics during the near future
Microstructure mapping: a new method for imaging deformation-induced microstructural features of ice on the grain scale
Eicosanoid Control Over Antigen Presenting Cells in Asthma
Asthma is a common lung disease affecting 300 million people worldwide. Allergic asthma is recognized as a prototypical Th2 disorder, orchestrated by an aberrant adaptive CD4+ T helper (Th2/Th17) cell immune response against airborne allergens, that leads to eosinophilic inflammation, reversible bronchoconstriction, and mucus overproduction. Other forms of asthma are controlled by an eosinophil-rich innate ILC2 response driven by epithelial damage, whereas in some patients with more neutrophilia, the disease is driven by Th17 cells. Dendritic cells (DCs) and macrophages are crucial regulators of type 2 immunity in asthma. Numerous lipid mediators including the eicosanoids prostaglandins and leukotrienes influence key functions of these cells, leading to either pro- or anti-inflammatory effects on disease outcome. In this review, we will discuss how eicosanoids affect the functions of DCs and macrophages in the asthmatic lung and how this leads to aberrant T cell differentiation that causes disease
Cellular networks controlling Th2 polarization in allergy and immunity
In contrast to the development of Th1 (type 1 T helper cells), Th17 and Treg (regulatory T cells), little is known of the mechanisms governing Th2 development, which is important for immunity to helminths and for us to understand the pathogenesis of allergy. A picture is emerging in which mucosal epithelial cells instruct dendritic cells to promote Th2 responses in the absence of IL-12 (interleukin 12) production and provide instruction through thymic stromal lymphopoieitin (TSLP) or granulocyte-macrophage colony stimulating factor (GM-CSF). At the same time, allergens, helminths and chemical adjuvants elicit the response of innate immune cells like basophils, which provide more polarizing cytokines and IL-4 and reinforce Th2 immunity. This unique communication between cells will only be fully appreciated if we study Th2 immunity in vivo and in a tissue-specific context, and can only be fully understood if we compare several models of Th2 immune response induction
Aspergillus and the Lung
The filamentous fungus Aspergillus causes a wide spectrum of diseases in the human lung, with Aspergillus fumigatus being the most pathogenic and allergenic subspecies. The broad range of clinical syndromes that can develop from the presence of Aspergillus in the respiratory tract is determined by the interaction between host and pathogen. In this review, an oversight of the different clinical entities of pulmonary aspergillosis is given, categorized by their main pathophysiological mechanisms. The underlying immune processes are discussed, and the main clinical, radiological, biochemical, microbiological, and histopathological findings are summarized.</p
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