Linear and angular momentum of electromagnetic fields generated by an arbitrary distribution of charge and current densities at rest

Starting from Stratton-Panofsky-Phillips-Jefimenko equations for the electric and magnetic fields generated by completely arbitrary charge and current density distributions at rest, we derive far-zone approximations for the fields, containing all components, dominant as well as sub-dominant. Using these approximate formulas, we derive general formulas for the total electromagnetic linear momentum and angular momentum, valid at large distances from arbitrary, non-moving charge and current sources.Comment: Six pages, one figure. Errors correcte

Storming Majorana's Tower with OAM states of light in a plasma

We extend the relationship between mass and spin angular momentum, described by the bosonic spectrum of positive definite mass particles of the Majorana solution to the Dirac equation, to photons that acquire an effective Proca mass through the Anderson-Higgs mechanism when they propagate in a plasma. In an earlier paper we showed that if the plasma is structured, it can impart orbital angular momentum (OAM) to the photons that reduces the total Proca photon mass. Here we show, through a generalisation of Majorana's solution, that photons with OAM in a plasma cannot assume negative squared mass states. This means that there exist interesting analogies with Quantum Gravity or General Relativity models involving a modified action of the Lorentz group.Comment: 4 pages; Corrected, updated versio

Chemical analyses of extremely degraded wood using analytical pyrolysis and inductively coupled plasma atomic emission spectroscopy

Alum-treated archaeological woods from the Oseberg collection, excavated and treated in the early 1900s demonstrate an extreme deterioration, only discovered in the past decade. This research was aimed at understanding the characteristics of the naturally aged material through chemical analyses of both organic and inorganic components, in order to provide information for the preservation/conservation of these precious objects. Analytical pyrolysis-gas chromatography/mass spectrometry with in situ silylation using hexamethyldisilazane (Py(HMDS)-GC/MS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were used to investigate a set of samples of alum-treated archaeological wood and untreated archaeological wood. Sound woods of the same species were also analysed in order to compare the results. Results from Py(HMDS)-GC/MS analyses of alum-treated woods from Oseberg showed an extreme depletion of carbohydrates and a highly deteriorated lignin network. The majority of the lignin had undergone oxidation reactions, illustrated by high relative amounts of acidic pyrolysis products. In particular, p-hydroxy-benzoic acid was detected for the first time as a degradation product of archaeological wood. Results from ICP-AES showed variable concentrations of aluminium and potassium from the alum treatment, as well as iron, copper, zinc and calcium. The extent of oxidation observed by Py(HMDS)-GC/MS appeared to correlate with relative amounts of iron and calcium in the samples, which may suggest that degradation promoted by iron compounds is inhibited in the presence of calcium compounds. The results obtained for a sample of archaeological wood treated with alum salts five years ago showed that chemical deterioration of lignin had already begun, mainly involving depolymerisation reactions, though only a slight increase in oxidation was evident. In addition to increased insight into potential deterioration reactions, occurring in a complex material such as alum-treated archaeological wood, it was possible to relate the degree of chemical degradation of the Oseberg woods to their visual condition (observed with the naked eye). © 2015 Elsevier B.V

Photon Orbital Angular Momentum and Mass in a Plasma Vortex

We analyse the Anderson-Higgs mechanism of photon mass acquisition in a plasma and study the contribution to the mass from the orbital angular momentum acquired by a beam of photons when it crosses a spatially structured charge distribution. To this end we apply Proca-Maxwell equations in a static plasma with a particular spatial distribution of free charges, notably a plasma vortex, that is able to impose orbital angular momentum (OAM) onto light. In addition to the mass acquisition of the conventional Anderson-Higgs mechanism, we find that the photon acquires an additional mass from the OAM and that this mass reduces the Proca photon mass.Comment: Four pages, no figures. Error corrections, improved notation, refined derivation

Lymph Node Lymphatic Endothelial Cell Expansion and Contraction and the Programming of the Immune Response

Lymphatic endothelial cells (LECs) form the structure of the lymphatic vessels and the sinuses of the lymph nodes, positioning them to be key players in many different aspects of the immune response. Following an inflammatory stimulus, LECs produce chemokines that recruit immune cells to the lymph nodes. The recruitment of immune cells aids in the coordination of both LEC and lymph node expansion and contraction. More recent data has demonstrated that to coordinate LEC division and death, cell surface molecules, such as PD-L1 and interferon receptors, are required. During homeostasis, LECs use PD-L1 to maintain peripheral tolerance by presenting specific peripheral tissue antigens in order to eliminate tissue specific responses. LECs also have the capacity to acquire, present, and exchange foreign antigens following viral infection or immunization. Here we will review how lymph node LECs require immune cells to expand and contract in response to an immune stimulus, the factors involved and how direct LEC-immune cell interactions are important for programming immunity

Spin-polarized electron beam generation in the colliding-pulse injection scheme

Employing colliding-pulse injection has been shown to enable high-quality electron beams to be generated from laser-plasma accelerators. Here by leveraging test particle simulations, Hamiltonian analysis, and multidimensional particle-in-cell (PIC) simulations, we lay the theoretical framework of spin-polarized electron beam generation in the colliding-pulse injection scheme. Furthermore, we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80\% polarization and tens pC charge with commercial 10-TW-class laser systems.Comment: 11 pages, 10 figure

REAPOWER – USE OF DESALINATION BRINE FOR POWER PRODUCTION THROUGH REVERSE ELECTRODIALYSIS

Salinity Gradient Power (SGP) represents a viable renewable energy source associated with the mixing of two solutions of different salinities. Reverse Electrodialysis (SGP-RE or RED) is a promising technology to exploit this energy source and directly generate electricity. However, although the principle of this technology is well known since several years, further R&D efforts are still necessary in order to explore the real potential of the SGP-RE process. With this regard, the aim of the REAPower project (www.reapower.eu) is the development of an innovative system for power production by SGP-RE process, using sea (or brackish) water as diluted solution and brine as concentrate. The use of sea or brackish water (instead of fresh water) as diluate allows reducing the electrical resistance of the diluate compartment, increasing the achievable output power. This work presents the R&D activities carried out so far within the REAPower project, particularly focusing on the relevant progresses in membranes development, stack design and process modelling. An extensive experimental campaign has been performed on a lab-scale unit, allowing to reach a power density among the highest so far presented in the open literature. These results provided useful information for the final goal of the project, i.e. the construction of the first SGP-RE system on a small pilot-scale, in order to demonstrate the feasibility of the future scale-up for this technology

The molecular size continuum of soil organic phosphorus and its chemical associations

The chemical nature of most organic P (Porg) in soil remains ‘unresolved’ but is accounted for by a broad signal in the phosphomonoester region of solution 31P nuclear magnetic resonance (NMR) spectra. The molecular size range of this broad NMR signal and its molecular structure remain unclear. The aim of this study was to elucidate the chemical nature of Porg with increasing molecular size in soil extracts combining size exclusion chromatography (SEC) with solution 31P NMR spectroscopy. Gel-filtration SEC was carried out on NaOH-EDTA extracts of four soils (range 238-1135 mg Porg/kgsoil) to collect fractions with molecular sizes of 70 kDa. These were then analysed by NMR spectroscopy. Organic P was detected across the entire molecular size continuum from 70 kDa. Concentrations of Porg in the >10kDa fraction ranged from 107 to 427 mg P/kgsoil and exhibited on average three to four broad signals in the phosphomonoester region of NMR spectra. These broad signals were most prominent in the 10-20 and 20-50 kDa fractions, accounting for on average 77 % and 74 % of total phosphomonoesters, respectively. Our study demonstrates that the broad signal is present in all investigated molecular size fractions and comprises on average three to four components of varying NMR peak line width (20 to 250 Hz). The stereoisomers myo- and scyllo-inositol hexakisphosphates (IP6) were also present across multiple molecular size ranges but were predominant in the 5-10 kDa fraction. The proportion of IP associated with large molecular size fractions >10 kDa was on average 23 % (SD=39 %) of total IP across all soils. These findings suggest that stabilisation of IP in soil includes processes associated with the organic phase

Dissecting accretion and outflows in accreting white dwarf binaries

This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of accreting white dwarfs. For a summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large Observatory for X-ray Timin