Radiative transfer in a spherical, emitting, absorbing and anisotropically scattering medium

The atmospheres of planets (including Earth) and the outer layers of stars have often been treated in radiative transfer as plane-parallel media, instead of spherical shells, which can lead to inaccuracy, e.g. limb darkening. We give an exact solution of the radiative transfer specific intensity at all points and directions in a finite spherical medium having arbitrary radial spectral distribution of: source (temperature), absorption, emission and anisotropic scattering. The power and efficiency of the method stems from the spherical numerical gridding used to discretize the transfer equations prior to matrix solution: the wanted ray and the rays which scatter into it both have the same physico-geometric structure. Very good agreement is found with an isotropic astrophysical benchmark (Avrett & Loeser, 1984). We introduce a specimen arbitrary forward-back-side phase scattering function for future comparisons. Our method directly and exactly addresses spherical symmetry with anisotropic scattering, and could be used to study the Earth's climate, nuclear power (neutron diffusion) and the astrophysics of stars and planets.Comment: 8 pages, 2 figures, spherical radiative transfer: stellar, planetary, terrestia

Skin Barrier Immunity and Ageing

The skin is the outermost layer of the body with an extensive surface area of approximately 1·8 m2, and is the first line of defence against a multitude of external pathogens and environmental insults. The skin also has important homeostatic functions such as reducing water loss and contributing to thermoregulation of the body. The structure of the skin and its cellular composition work in harmony to prevent infections and to deal with physical and chemical challenges from the outside world. In this review, we discuss how the structural cells such as keratinocytes, fibroblasts and adipocytes contribute to barrier immunity. We also discuss specialized immune cells that are resident in steady‐state skin including mononuclear phagocytes, such as Langerhans cells, dermal macrophages and dermal dendritic cells in addition to the resident memory T cells. Ageing results in an increased incidence of cancer and skin infections. As we age, the skin structure changes with thinning of the epidermis and dermis, increased water loss, and fragmentation of collagen and elastin. In addition, the skin immune composition is altered with reduced Langerhans cells, decreased antigen‐specific immunity and increased regulatory populations such as Foxp3+ regulatory T cells. Together, these alterations result in decreased barrier immunity in the elderly, explaining in part their increased susceptiblity to cancer and infections

Assessing the Role of Compaction in the Formation of Adcumulates: a Microstructural Perspective

The formation of adcumulates necessitates the continued growth of primocrysts down to low porosities. Gravitationally driven viscous compaction at the base of a crystal mushy layer on the magma chamber floor, driven by the weight of the mushy layer itself, is commonly suggested as a significant process acting to drive out interstitial liquid and promote adcumulate formation. Compaction necessitates viscous deformation, by either dislocation creep or diffusion-controlled processes such as pressure-solution: many studies suggest that the foliations preserved in cumulates are a consequence of recrystallization during compaction, completely overprinting primary magmatic fabrics. We test the compaction hypothesis by looking for microstructural evidence of viscous deformation. A detailed examination of cumulates from the Skaergaard intrusion, East Greenland, demonstrates only limited crystal plastic deformation, with no correlation between the extent of dislocation creep and the calculated volume fraction of trapped liquid left in the cumulates. Although the evidence for diffusion-controlled deformation is often cryptic, there is an anti-correlation between apparent aspect ratio of plagioclase and the extent of adcumulate crystallization, contradicting previous hypotheses involving transposition of original magmatic fabrics by dissolution–reprecipitation. This is supported by the spatial distribution of compositional zoning in plagioclase, which demonstrates that pressure-solution or related diffusion-controlled processes were insufficient to obscure primary magmatic fabrics. The Skaergaard adcumulates did not form by viscous compaction. Instead we suggest that they formed by primary processes involving mass transport in a thin mushy layer. Compaction is most likely to occur in slowly cooled intrusions in which the bulk magma crystallizes abundant dense minerals. We present preliminary observations of microstructures in norites from the lower Main Zone of the Bushveld Intrusion, South Africa, and in plagioclase-rich cumulates from the Fe–Ti oxide-rich Baima Intrusion, SW China. The evidence for dislocation creep in both intrusions is unambiguous, although deformation was insuffi- cient to obliterate all traces of the primary magmatic fabrics and unlikely to have been sufficient to significantly reduce the volume of interstitial liquid.This work was supported by the Natural Environment Research Council [grant numbers NE/J021520/1 and NE/M000060/1] and a Royal Society International Joint Project grant. Z.V. is supported by a Marie SkłodowskaCurie Individual European Fellow grant

The creation and evolution of crystal mush in Upper Zone of the Rustenburg Layered Suite, Bushveld Complex, South Africa

The Upper Zone of the Rustenburg Layered Suite of the Bushveld Complex contains the world’s largest Fe-Ti-V±P deposit and formed from the last major injection of magma into the chamber. Quantitative textural analysis of Upper Zone rocks was undertaken to constrain the processes operating during mush formation and solidification, focussing on horizons with the greatest density contrast to isolate the effects of gravitational loading. We examined three magnetitite layers, together with their underlying and overlying anorthosites. The similarity of microstructures in anorthosites above and below the dense magnetitite layers suggests that the rocks were not affected by viscous compaction driven by gravitational loading. The magnetitite cumulate layers formed by crystal accumulation from a mobile crystal slurry dominated by the Fe-rich conjugate of unmixed immiscible liquid. We suggest a new mechanism of crystal nucleation in deforming crystal-rich systems, driven by undercooling caused by cavitation as grains slide past each other during simple shear. We propose that the super-solidus deformation recorded in these rocks was caused by prolonged regional subsidence of the magma chamber at Upper Zone times

The Skaergaard trough layering: sedimentation in a convecting magma chamber.

The upper parts of the floor cumulates of the Skaergaard Intrusion, East Greenland, contain abundant features known as troughs. The troughs are gently plunging synformal structures comprising stacks of crescentic modally graded layers with a sharply defined mafic base that grades upward into plagioclase-rich material. The origin of the troughs and layering is contentious, attributed variously to deposition of mineral grains by magmatic currents descending from the nearby walls, or to in situ development by localised recrystallisation during gravitationally-driven compaction. They are characterised by outcrop-scale features such as mineral lineations parallel to the trough axis, evidence of erosion and layer truncation associated with migration of the trough axis, and disruption of layering by syn-magmatic slumping. A detailed microstructural study of the modal trough layers, using electron backscatter diffraction together with geochemical mapping, demonstrates that these rocks do not record evidence for deformation by either dislocation creep or dissolution-reprecipitation. Instead, the troughs are characterised by the alignment of euhedral plagioclase crystals with unmodified primary igneous compositional zoning. We argue that the lineations and foliations are, therefore, a consequence of grain alignment during magmatic flow. Post-accumulation amplification of the modal layering occurred as a result of differential migration of an unmixed immiscible interstitial liquid, with upwards migration of the Si-rich conjugate into the plagioclase-rich upper part of the layers, whereas the Fe-rich immiscible conjugate remained in the mafic base. Both field and microstructure evidence support the origin of the troughs as the sites of repeated deposition from crystal-rich currents descending from the nearby chamber walls

On functions of neurotrophic factors in taste buds and teeth

Background: Chemosensory disorders affect approximately 15% of the U.S. population and an estimated 200,000 individuals visit a doctor each year for problems with their ability to taste or smell (NIDCD). Among the common causes of taste problems are radiation therapy, chemotherapy, exposure to certain chemicals and medications, head trauma and surgical injuries. Tastants are detected by taste buds, which are specialized collections of cells. Taste bud development and innervation has been an active research front and several key molecules involved in these processes have been elucidated. Neurotrophins, in particular brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) were among the first to be identified as playing a role in taste buds. BDNF and NT-3 are expressed in developing and adult rodent tongues in a temporospatially specific manner. BDNF mRNA is found in the gustatory epithelium during development and in adult taste buds, NT-3 mRNA in the surrounding epithelium in rodents. Neurotrophins are also expressed in a temporospatially specific manner during tooth morphogenesis. Nerve growth factor (NGF), BDNF and glial cell line-derived neurotrophic factor (GDNF) are expressed in developing rodent teeth. Aims: To examine the expression of mRNA encoding neurotrophic factors in the developing human taste system and teeth, to assess the role of neurotrophic factors in the formation and innervation of taste buds and teeth, and to explore possible consequences of neurotrophic factor expression in cultured dental pulp cells (DPCs). Results: Neurotrophic factor expression patterns are described in the developing human tongue and compared to those of rodents. BDNF was found in the first-trimester in the same areas as in rodents; developing gustatory epithelium and taste buds, and in additional areas such as the subepithelial mesenchyme. Human NT-3 mRNA expression patterns were largely similar to those of rodents, except that taste buds also expressed NT-3 mRNA during development and in adults. In both rodents and humans, BDNF was expressed prior to innervation of gustatory papillae, and thus serves as a very early marker of the gustatory epithelium. Our study showed wider expression patterns of both BDNF and NT-3 in the human gustatory system (paper I) compared to rodents. Next, we showed that taste papillae in BDNF/NT-3 double KO mice were smaller and less innervated compared to BDNF-/- mice, indicating specific gustatory roles for both neurotrophins (paper V). Studies of developing human teeth showed that NGF, BDNF, NT-3, neurotrophin-4 (NT-4), GDNF and neurturin (NTN) were expressed in the tooth organ and surrounding mesenchyme (paper III). Interactions of neurotrophic factors from the dental pulp and trigeminal, motor and dopamine (DA) neurons were analyzed. DPCs promoted survival and neurite outgrowth from trigeminal neurons in cocultures, and prolonged neural survival in vitro. DPCs also promoted motoneuron survival in a rodent model of spinal cord injury (paper II), as well as the survival of embryonic DA neurons in vitro (paper IV). BDNF is the main neurotrophic factor in the gustatory system, but NT-3 plays a role as well in both humans and rodents, which knockout studies were able to detect. The tooth provides an excellent model to study molecular events in cells during organ formation, and to examine how neurotrophic factors promote innervation during development

Insights Into Magma Chamber Processes From the Relationship Between Fabric and Grain Shape in Troctolitic Cumulates

The strength of foliations defined by shape preferred orientation of plagioclase in troctolitic cumulates from the Layered Series of the Skaergaard intrusion, and the Rum Eastern Layered Intrusion, increases as the grains become more tabular, due either to the greater propensity of highly non-equant grains to be re-arranged by magmatic currents or tectonic disruption of poorly consolidated mush, or by the effects of a pre-existing shape preferred orientation on final grain shape in fully solidified rocks. The stratigraphic evolution of grain shape, microstructures and fabrics in the lowest 320 m of the Skaergaard Layered Series records the progressive inflation of the chamber to its final size. During the earliest stages of solidification, the extent of in situ nucleation and growth on the chamber floor decreased upward through the stratigraphy, due to the development of a thermally insulating blanket of mush on the floor. An upward increase in foliation strength as the chamber inflated to its final size was a result of the increasing strength of convection of the bulk magma and an increasing contribution to the floor mush of crystals derived from the walls of the enlarging magma chamber. Plagioclase in the troctolites in the open-system magma chamber of the Rum Eastern Layered Intrusion is generally more equant than that in the Skaergaard intrusion, perhaps related to the slower crystal growth on the margins of the continuously replenished Rum chamber. Significant sub-solidus modification of original igneous microstructures is observed in Rum troctolites from parts of the stratigraphy recording frequent replenishment events

Impact of Zostavax Vaccination on T-Cell Accumulation and Cutaneous Gene Expression in the Skin of Older Humans After Varicella Zoster Virus Antigen-Specific Challenge

Background The live attenuated vaccine Zostavax was developed to prevent varicella zoster virus (VZV) reactivation that causes herpes zoster (shingles) in older humans. However, the impact of vaccination on the cutaneous response to VZV is not known. Methods We investigated the response to intradermal VZV antigen challenge before and after Zostavax vaccination in participants >70 years of age by immunohistological and transcriptomic analyses of skin biopsy specimens collected from the challenge site. Results Vaccination increased the proportion of VZV-specific CD4+ T cells in the blood and promoted the accumulation of both CD4+ and CD8+ T cells in the skin after VZV antigen challenge. However, Zostavax did not alter the proportion of resident memory T cells (CD4+ and CD8+) or CD4+Foxp3+ regulatory T cells in unchallenged skin. After vaccination, there was increased cutaneous T-cell proliferation at the challenge site and also increased recruitment of T cells from the blood, as indicated by an elevated T-cell migratory gene signature. CD8+ T-cell–associated functional genes were also highly induced in the skin after vaccination. Conclusion Zostavax vaccination does not alter the abundance of cutaneous resident memory T cells but instead increases the recruitment of VZV-specific T cells from the blood and enhances T-cell activation, particularly cells of the CD8+ subset, in the skin after VZV antigen challenge