Using airborne LiDAR Survey to explore historic-era archaeological landscapes of Montserrat in the eastern Caribbean

This article describes what appears to be the first archaeological application of airborne LiDAR survey to historic-era landscapes in the Caribbean archipelago, on the island of Montserrat. LiDAR is proving invaluable in extending the reach of traditional pedestrian survey into less favorable areas, such as those covered by dense neotropical forest and by ashfall from the past two decades of active eruptions by the Soufrière Hills volcano, and to sites in localities that are inaccessible on account of volcanic dangers. Emphasis is placed on two aspects of the research: first, the importance of ongoing, real-time interaction between the LiDAR analyst and the archaeological team in the field; and second, the advantages of exploiting the full potential of the three-dimensional LiDAR point cloud data for purposes of the visualization of archaeological sites and features

Вычисление потенциалов межатомного взаимодействия в металлах при наличии ионизационных процессов, вызванных излучением

Объектом исследования является изменение межатомного взаимодействия в металлах при ионизации и возбуждении электронной подсистемы. Цель работы – изучение взаимодействия заряженных частиц с твердотельными структурами с точки зрения анализа эффектов, остающихся в настоящее время недостаточно изученными, а именно, формы потенциалов межатомного взаимодействия металлов при ионизации атомов и возбуждении электронов проводимости в области треков быстрых заряженных частиц и в зоне релаксации возбужденных состояний. На основе псевдопотенциального подхода проанализировано поведение потенциалов межатомного взаимодействия в алюминии в условиях возбуждения электронной подсистемы.The object of the study is the change in the interatomic interaction in metals during ionization and excitation of the electronic subsystem. The aim of the work is to study the interaction of charged particles with solid-state structures from the point of view of analyzing the effects that remain currently insufficiently studied, namely, the forms of the potentials of the interatomic interaction of metals during the ionization of atoms and the excitation of conduction electrons in the region of the tracks of fast charged particles and in the relaxation zone of excited states. The behavior of the interatomic interaction potentials in aluminum under the conditions of excitation of the electronic subsystem is analyzed on the basis of the pseudopotential approach

Development of a lectin-affinity chromatography step for the downstream processing of influenza virus vaccines

Influenza remains due to its annual death rate and potential to cause pandemics a major public health concern. Efforts to control the annual spread of influenza have centered on prophylactic vaccinations. Human influenza vaccines are traditionally produced in embryonated hen s eggs. However, major constraints with this method, e.g. allergic reactions induced by egg proteins and lack of scalability have lead to the development of cell culture based production processes. In recent years, several continuous cell lines such as the Madin Darby canine kidney (MDCK) or the African green monkey kidney Vero cells have been successfully established for the production of influenza vaccines in cell culture. These processes require the modification of existing but also the development of new downstream strategies to account for the changed upstream technology. Downstream processing of biological products is conventionally subdivided into three steps: capture or concentration, separation or fractionation and polishing. The capture step is commonly the most expensive unit operation. Hence, the efficiency of this step has a large impact on the total process economics. The presented study focuses on the development of a proficient capture step based on lectin-affinity chromatography. Lectins are a class of carbohydrate specific proteins of non-immune origin that have a selective affinity for a carbohydrate or a group of carbohydrates. Immobilized lectins have been used successfully for many years to separate and isolate glycoconjugates, polysaccharides, soluble cell components, and cells containing glycoproteins with specific carbohydrate structures on its surface. The influenza A virus contains two spike glycoproteins on its surface: hemagglutinin (HA) and neuraminidase (NA). HA is the most abundant surface protein. It is a trimeric glycoprotein containing per subunit 3 to 9 N-linked glycosylation sites depending on the viral strain. Here the influenza A/PR/8/34 virus has been selected as a model. The HA molecule of this particular virus contains according to the NetNGlyc 1.0 Server prediction six glycosylation sites. Detailed analysis of these sites and their individual glycan structures are presently performed. Based on preliminary structural glycan analysis studies and literature data several HA-binding lectins are selected for a pre-screening via lectin-blots. The most promising lectinblot results are obtained from lectins specific for terminal galactose e.g. Erythrina cristagalli (ECL), Arachis hypogaea (PNA). Lectins, by which lectin-blot analysis suggests an interaction with viral membrane proteins, are currently screened for their suitability as an affinity matrix ligand. Therefore, centrifuged cultivation broths of influenza A/PR/8/34 virus infected MDCK cells are applied to various agaroseimmobilized lectins. Components interfering with the immobilized lectins are selectively adsorbed. Non or weak binding components are washed from the column. Subsequently, bound components are dissociated from the lectin by competitive elution with suitable hapten carbohydrates. This fraction contains the influenza virus particles and virally encoded membrane proteins, which have to be further processed for vaccine manufacturing. The extend of the subsequent purification depends on the specificity of the lectin binding to virally encoded surface proteins. Lectins with weak or no interaction with host cell proteins or medium components and strong interaction with viral membrane glycoproteins represent a powerful tool to concentrate and purify viral surface proteins from contaminating nucleic acids, medium components, and non-virally encoded host cell proteins

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum : STEREO observations

Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs) in the vicinity of corotating interaction regions (CIRs) during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used), but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream), as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1) the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2) that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to CIRs

Multipoint connectivity analysis of the May 2007 solar energetic particle events

In May of 2007, the STEREO Ahead and Behind spacecraft, along with the ACE spacecraft situated between the two STEREO spacecraft, observed two small solar energetic particle (SEP) events. STEREO-A and -B observed nearly identical time profiles in the 19 May event, but in the 23 May event, the protons arrived significantly earlier at STEREO-A than at STEREO-B and the time-intensity profiles were markedly different. We present SEP anisotropy, suprathermal electron pitch angle and solar wind data to demonstrate distortion in the magnetic field topology produced by the passage of multiple interplanetary coronal mass ejections on 22 and 23 May, causing the two spacecraft to magnetically connect to different points back at the Sun. This pair of events illustrates the power of multipoint observations in detailed interpretation of complex events, since only a small shift in observer location results in different magnetic field line connections and different SEP time-intensity profiles

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations

Copyright © Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 LicenseOpen Access journalPrevious work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs) in the vicinity of corotating interaction regions (CIRs) during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used), but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream), as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1) the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2) that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to CIRs

Temporal Evolution of the Solar-Wind Electron Core Density at Solar Minimum by Correlating SWEA Measurements from STEREO A and B

The twin STEREO spacecraft provide a unique tool to study the temporal evolution of the solar-wind properties in the ecliptic since their longitudinal separation increases with time. We derive the characteristic temporal variations at ∼ 1 AU between two different plasma parcels ejected from the same solar source by excluding the spatial variations from our datasets. As part of the onboard IMPACT instrument suite, the SWEA electron experiment provides the solar-wind electron core density at two different heliospheric vantage points. We analyze these density datasets between March and August 2007 and find typical solar minimum conditions. After adjusting for the theoretical time lag between the two spacecraft, we compare the two density datasets. We find that their correlation decreases as the time difference increases between two ejections. The correlation coefficient is about 0.80 for a time lag of a half day and 0.65 for two days. These correlation coefficients from the electron core density are somewhat lower than the ones from the proton bulk velocity obtained in an earlier study, though they are still high enough to consider the solar wind as persistent after two days. These quantitative results reflect the variability of the solar-wind properties in space and time, and they might serve as input for solar-wind models

Temporal Evolution of the Solar Wind Bulk Velocity atSolar Minimum by Correlating the STEREO A andBPLASTIC Measurements

The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45° per year, providing a unique tool to study the temporal evolution of the solar wind. We analyze the solar wind bulk velocity measured by the two PLASTIC plasma instruments onboard the two STEREO spacecraft. During the first half year of our measurements (March - August 2007) we find the typical alternating slow and fast solar wind stream pattern expected at solar minimum. To evaluate the temporal evolution of the solar wind bulk velocity we exclude the spatial variations and calculate the correlation between the solar wind bulk velocity measured by the two spacecraft. We account for the different spacecraft positions in radial distance and longitude by calculating the corresponding time lag. After adjusting for this time lag we compare the solar wind bulk velocity measurements at the two spacecraft and calculate the correlation between the two time-shifted datasets. We show how this correlation decreases as the time difference between two corresponding measurements increases. As a result, the characteristic temporal changes in the solar wind bulk velocity can be inferred. The obtained correlation is 0.95 for a time lag of 0.5 days and 0.85 for 2 day

Influenza C virus NS1 protein counteracts RIG-I-mediated IFN signalling

The nonstructural proteins 1 (NS1) from influenza A and B viruses are known as the main viral factors antagonising the cellular interferon (IFN) response, inter alia by inhibiting the retinoic acid-inducible gene I (RIG-I) signalling. The cytosolic pattern-recognition receptor RIG-I senses double-stranded RNA and 5'-triphosphate RNA produced during RNA virus infections. Binding to these ligands activates RIG-I and in turn the IFN signalling. We now report that the influenza C virus NS1 protein also inhibits the RIG-I-mediated IFN signalling. Employing luciferase-reporter assays, we show that expression of NS1-C proteins of virus strains C/JJ/50 and C/JHB/1/66 considerably reduced the IFN-β promoter activity. Mapping of the regions from NS1-C of both strains involved in IFN-β promoter inhibition showed that the N-terminal 49 amino acids are dispensable, while the C-terminus is required for proper modulation of the IFN response. When a mutant RIG-I, which is constitutively active without ligand binding, was employed, NS1-C still inhibited the downstream signalling, indicating that IFN inhibitory properties of NS1-C are not necessarily linked to an RNA binding mechanism

Quantum Fluctuations Driven Orientational Disordering: A Finite-Size Scaling Study

The orientational ordering transition is investigated in the quantum generalization of the anisotropic-planar-rotor model in the low temperature regime. The phase diagram of the model is first analyzed within the mean-field approximation. This predicts at $T=0$ a phase transition from the ordered to the disordered state when the strength of quantum fluctuations, characterized by the rotational constant $\Theta$, exceeds a critical value $\Theta_{\rm c}^{MF}$. As a function of temperature, mean-field theory predicts a range of values of $\Theta$ where the system develops long-range order upon cooling, but enters again into a disordered state at sufficiently low temperatures (reentrance). The model is further studied by means of path integral Monte Carlo simulations in combination with finite-size scaling techniques, concentrating on the region of parameter space where reentrance is predicted to occur. The phase diagram determined from the simulations does not seem to exhibit reentrant behavior; at intermediate temperatures a pronounced increase of short-range order is observed rather than a genuine long-range order.Comment: 27 pages, 8 figures, RevTe