The dark side of solar photospheric G-band bright points

Bright small-scale magnetic elements found mainly in intergranular lanes at the solar surface are named bright points (BPs). They show high contrasts in Fraunhofer G-band observations and are described by nearly vertical slender flux tubes or sheets. A recent comparison between BP observations in the ultraviolet (UV) and visible spectral range recorded with the balloon-borne observatory SUNRISE and state-of-the-art magnetohydrodynamical (MHD) simulations revealed a kiloGauss magnetic field for 98% of the synthetic BPs. Here we address the opposite question, namely which fraction of pixels hosting kiloGauss fields coincides with an enhanced G-band brightness. We carried out 3D radiation MHD simulations for three magnetic activity levels (corresponding to the quiet Sun, weak and strong plage) and performed a full spectral line synthesis in the G-band. Only 7% of the kiloGauss pixels in our quiet-Sun simulation coincide with a brightness lower than the mean quiet-Sun intensity, while 23% of the pixels in the weak-plage simulation and even 49% in the strong-plage simulation are associated with a local darkening. Dark strong-field regions are preferentially found in the cores of larger flux patches that are rare in the quiet Sun, but more common in plage regions, often in the vertices of granulation cells. The significant brightness shortfall in the core of larger flux patches coincide with a slight magnetic field weakening. KiloGauss elements in the quiet Sun are on average brighter than similar features in plage regions. Almost all strong-field pixels display a more or less vertical magnetic field orientation. Hence in the quiet Sun, G-band BPs correspond almost one-to-one with kiloGauss elements. In weak plage the correspondence is still very good, but not perfect.Comment: Accepted for publication in Astronomy & Astrophysic

Brightness of Solar Magnetic Elements as a Function of Magnetic Flux at High Spatial Resolution

We investigate the relationship between the photospheric magnetic field of small-scale magnetic elements in the quiet Sun (QS) at disc centre, and the brightness at 214 nm, 300 nm, 313 nm, 388 nm, 397 nm, and at 525.02 nm. To this end we analysed spectropolarimetric and imaging time series acquired simultaneously by the IMaX magnetograph and the SuFI filter imager on-board the balloon-borne observatory Sunrise during its first science flight in 2009, with high spatial and temporal resolution. We find a clear dependence of the contrast in the near ultraviolet (NUV) and the visible on the line-of-sight component of the magnetic field, $B_{\rm LOS}$, which is best described by a logarithmic model. This function represents well the relationship between the Ca II H-line emission and $B_{\rm LOS}$, and works better than a power-law fit adopted by previous studies. This, along with the high contrast reached at these wavelengths, will help with determining the contribution of small-scale elements in the QS to the irradiance changes for wavelengths below 388 nm. At all wavelengths including the continuum at 525.40 nm the intensity contrast does not decrease with increasing $B_{\rm LOS}$. This result also strongly supports that Sunrise has resolved small strong magnetic field elements in the internetwork, resulting in constant contrasts for large magnetic fields in our continuum contrast at 525.40 nm vs. $B_{\rm LOS}$ scatterplot, unlike the turnover obtained in previous observational studies. This turnover is due to the intermixing of the bright magnetic features with the dark intergranular lanes surrounding them

Complete sequence of HLA-B27 cDNA identified through the characterization of structural markers unique to the HLA-A, -B, and -C allelic series

Antigen HLA-B27 is a high-risk genetic factor with respect to a group of rheumatoid disorders, especially ankylosing spondylitis. A cDNA library was constructed from an autozygous B-cell line expressing HLA-B27, HLA-Cw1, and the previously cloned HLA-A2 antigen. Clones detected with an HLA probe' were isolated and sorted into homology groups by differential hybridization and restriction maps. Nucleotide sequencing allowed the unambiguous assignment of cDNAs to HL4-A, -B, and -C loci. The HLA-B27 mRNA has the structural features and the codon variability typical of an HLA class I transcript but it specifies two uncommon amino acid replacements: a cysteine in position 67 and a serine in position 131. The latter substitution may have functional consequences, because it occurs in a conserved region and at a position invariably occupied by a species-specific arginine in humans and lysine in mice. The availability of the complete sequence of HLA-B27 and of the partial sequence of HLA-Cw1 allows the recognition of locus-specific sequence markers, particularly, but not exclusively, in the transmembrane and cytoplasmic domains

Investigations of small-scale magnetic features on the solar surface

Solar activity is controlled by the magnetic field, which also causes the variability of the solar irradiance that in turn is thought to influence the climate on Earth. The magnetic field manifests itself in the form of structures of largely different sizes. This thesis concentrates on two types of the smallest known magnetic features: The first part studies the properties of umbral dots, dot-like bright features in the dark umbra of a sunspot. The obtained umbral dot properties provide a remarkable confirmation of the results of recent magneto-hydrodynamical simulations. Observations as well as simulations show that umbral dots differ from their surroundings mainly in the lowest photospheric layers, where the temperature is enhanced and the magnetic field is weakened. In addition, the interior of the umbral dots displays strong upflow velocities which are surrounded by weak downflows. This qualitative agreement further strengthens the interpretation of umbral dots as localized columns of overturning convection. The second part of the thesis investigates bright points, which are small-scale brightness enhancements in the darker intergranular lanes of the quiet Sun produced by magnetic flux concentrations. Observational data obtained by the balloon-borne solar telescope SUNRISE are used in this thesis. For the first time contrasts of bright points in the important ultraviolet spectral range are determined. A comparison of observational data with magneto-hydrodynamical simulations revealed a close correspondence, but only after effects due to the limited spectral and spatial resolution were carefully included. 98% of the synthetic bright points are found to be associated with a nearly vertical kilo-Gauss field.Comment: PhD thesis, Braunschweig University, 209 pages; ISBN 978-3-942171-73-1, uni-edition GmbH 201

Expression of the CD6 T lymphocyte differentiation antigen in normal human brain

Antigens shared by the immune and central nervous systems (CNS) have been described repeatedly. The present study reports the expression of the CD6 lymphocyte differentiation antigen in normal human brain evidenced by immunohistochemistry and Northern blot analysis. A panel of various anti-CD6 monoclonal antibodies (mabs) tested on serial cryostat sections identified CD6-positive cells randomly scattered in parenchyma of all examined brain areas. Northern blot analysis with a highly sensitive cRNA probe revealed a 3.1 kb CD6-specific mRNA in various brain regions, especially in basalganglia and cortex cerebellum. Staining with mabs raised against different hematopoietic cell types, as well as hybridization with probes specific for the ß- and y-T cell receptor (TCR) chains support the notion that CD6 is expressed by original brain cells. The nature of the CD6-positive cell type and possible functions of shared antigens in immune and nervous systems are discusse

Non-destructive testing of the parts manufactured by Direct Metal Laser Sintering

Published ThesisInterest in Additive Manufacturing (AM) has grown considerably in the past decades and industry has gained great benefits from this type of technology. The main advantages are: geometrical freedom that allows the design of parts with complex shape, which are difficult or impossible to produce by conventional technology; shortened design-to-product time; customization and the possibility to use several materials in one process. Direct Metal Laser Sintering (DMLS) is one of the most promising AM technologies that utilizes metal powders. Due to the layer-by-layer nature of powder delivery used in DMLS, the drawbacks are: surface quality and accuracy, high residual stress in as-built parts and porosity – all of which depend on the powder material, process-parameters, scanning and building strategies. This can result in a substantial deterioration of the mechanical properties of the products and their performance characteristics. For this reason, it is very important to identify defective parts before enrolling into service. Non-destructive testing (NDT) is effective for detection of internal defects without causing damage. NDT also covers a wide group of methods of analysis used to evaluate the properties of a material. NDT techniques like visual, acoustic, ultrasonic, thermal, X-ray and 3Dcomputed tomography (CT) inspections are now widely used for various industrial applications. For the analysis of material properties and the detection of defects, each of these methods uses different physical principles that have their advantages and disadvantages. In this study, some of the NDT techniques are evaluated in terms of their applicability to the inspection of parts manufactured by DMLS technology: Visual, Ultrasonic, Computed Tomography and Acoustic Emission inspection. Artificial defects were used to determine the feasibility of each NDT method. DMLS samples were produced containing a range of artificial defects. These samples were than subjected to each method and the results compared. A comparison between the amount of defect information obtained is made. It was shown that the nature of the sample; shape, size, material and the type of defects present plays a vital role in the selection of testing methods. Ultrasonic-Total Focus Method indicated that some defects are present upon testing relatively big samples with simple geometry. X-ray Computed Tomography showed some limitations with regard to the possibilities and the amount of defect detail, the only drawback being the cost and time involved. Acoustic Emission showed to be a promising method for production parts although it requires an initial time investment; thereafter it is a simple and easy way of detecting defective samples

Vertical flows and mass flux balance of sunspot umbral dots

A new Stokes inversion technique that greatly reduces the effect of the spatial point spread function of the telescope is used to constrain the physical properties of umbral dots (UDs). The depth-dependent inversion of the Stokes parameters from a sunspot umbra recorded with Hinode SOT/SP revealed significant temperature enhancements and magnetic field weakenings in the core of the UDs in deep photospheric layers. Additionally, we found upflows of around 960 m/s in peripheral UDs (i.e., UDs close to the penumbra) and $\approx$ 600 m/s in central UDs. For the first time, we also detected systematic downflows for distances larger than 200 km from the UD center that balance the upflowing mass flux. In the upper photosphere, we found almost no difference between the UDs and their diffuse umbral background.Comment: Accepted for publication in Astronomy and Astrophysic