Performance of Textured Metallized Teflon Coverings with High Diffuse Reflectance Coefficient in Low Earth Orbit on ISS

Процес модифікації поверхні текстуруванням був розроблений для лицьових поверхонь тефлоновим теплозахисних покриттів напиляних з тильного боку металізованим покриттям Silver-Inconel. Ці теплозахисні покриття приклеювалися на наружні стінки корпусів які містять фотокамери та світлове обладнання на Міжнародній космічній станції. Розроблена технологія, що включає процес текстурування поверхонь іонним пучком, який міняв морфологію поверхні з дзеркально-гладенькою до світло-розсіювання і молочно-білою, значно знизила дзеркальність терморегулювальних плівок, не надавши істотного впливу на їх термооптичні властивості. Космічна апаратура, покрита таким текстурированним тефлоном, піддавалася впливу факторів відкритого космосу в період з червня 2002 року по червень 2006 року і була повернута на Землю приблизно в листопаді 2006 року. Текстурований тефлон, що пробув у космосі 4 роки, продемонстрував стабільні робочі характеристики, зі значеннями коефіцієнта сонячної абсорбції (α) і коефіцієнта випромінювання (ε) і їх відносин α / ε які збереглися близькими до початкових значень, виміряних до польотів.A texturing surface modification process was developed for Silver- Inconel coated Teflon thermal protection coverings that were applied to a camera and light equipment on the International Space Station using an adhesive. The developed treatment that involves an ion-beam texturing process that changes the appearance of the surface in a controlled manner from a metallic-like and shiny to complete milky-white appearance reduced dramatically the specularity of Silver-Teflon thermal control films without significantly affecting their thermal optical properties. The space hardware covered with the textured back metallized Teflon was exposed to the open space environment between June 2002 and June 2006 and delivered back to earth around November 2006. Remarkable performance was demonstrated by the treated metallized Teflon with the solar absorptance and total emittance values and the α/ε ratio remaining very close to the original values as measured before the flights.Процесс модификации поверхности текстурированием был разработан для лицевых поверхностей тефлоновых теплозащитных покрытий напылённых с тыльной стороны металлизированным покрытием Silver-Inconel. Эти теплозащитные покрытия приклеивались на наружные стенки корпусов содержащих фотокамеры и световое оборудование на Международной космической станции. Разработанная технология, включающая процесс текстурирования поверхностей ионным пучком, который менял морфологию поверхности с зеркально-гладкой и блестящей до свето-рассеивающей и молочно-белой, значительно снизила зеркальность терморегулирующих пленок, не оказав существенного влияния на их термооптические свойства. Космическая аппаратура, покрытая таким текстурированным тефлоном, подвергалась воздействию факторам открытого космоса в период с июня 2002 года по июнь 2006 года и была возвращена на Землю примерно в ноябре 2006 года. Текстурированный тефлон, пробывший в космосе 4 года, продемонстрировал стабильные рабочие характеристики, со значениями коэффициентов солнечной абсорбции ( α) и коэффициента излучения ( ε) и их отношения α/ε сохранившимися близкими к исходным значениям, измеренным до полетов

Mechanism of thermally activated c-axis dissipation in layered High-Tc_c superconductors at high fields

We propose a simple model which explains experimental behavior of $c$-axis resistivity in layered High-T$_c$ superconductors at high fields in a limited temperature range. It is generally accepted that the in-plane dissipation at low temperatures is caused by small concentration of mobile pancake vortices whose diffusive motion is thermally activated. We demonstrate that in such situation a finite conductivity appears also in $c$-direction due to the phase slips between the planes caused by the mobile pancakes. The model gives universal relation between the components of conductivity which is in good agreement with experimental data.Comment: RevTeX, 4 pages, 2 Postscript figure

The BARD1 C-Terminal Domain Structure and Interactions with Polyadenylation Factor CstF-50†

The BARD1 N-terminal RING domain binds BRCA1 while the BARD1 C-terminal ankyrin and tandem BRCT repeat domains bind CstF-50 to modulate mRNA processing and RNAP II stability in response to DNA damage. Here we characterize the BARD1 structural biochemistry responsible for CstF- 50 binding. The crystal structure of the BARD1 BRCT domain uncovers a degenerate phosphopeptide binding pocket lacking the key arginine required for phosphopeptide interactions in other BRCT proteins.Small angle X-ray scattering together with limited proteolysis results indicates that ankyrin and BRCT domains are linked by a flexible tether and do not adopt a fixed orientation relative to one another. Protein pull-down experiments utilizing a series of purified BARD1 deletion mutants indicate that interactions between the CstF-50 WD-40 domain and BARD1 involve the ankyrin-BRCT linker but do not require ankyrin or BRCT domains. The structural plasticity imparted by the ANK-BRCT linker helps to explain the regulated assembly of different protein BARD1 complexes with distinct functions in DNA damage signaling including BARD1-dependent induction of apoptosis plus p53 stabilization and interactions. BARD1 architecture and plasticity imparted by the ANK-BRCT linker are suitable to allow the BARD1 C-terminus to act as a hub with multiple binding sites to integrate diverse DNA damage signals directly to RNA polymerase

Democratic cultural policy : democratic forms and policy consequences

The forms that are adopted to give practical meaning to democracy are assessed to identify what their implications are for the production of public policies in general and cultural policies in particular. A comparison of direct, representative, democratic elitist and deliberative versions of democracy identifies clear differences between them in terms of policy form and democratic practice. Further elaboration of these differences and their consequences are identified as areas for further research

The underscreened Kondo effect: a two S=1 impurity model

The underscreened Kondo effect is studied within a model of two impurities S=1 interacting with the conduction band and via an interimpurity coupling $K\vec{S_1}.\vec{S_2}$. Using a mean-field treatment of the bosonized Hamiltonian, we show that there is no phase transition, but a continuous cross-over versus K from a non Kondo behaviour to an underscreened Kondo one. For a small antiferromagnetic coupling (K>0), a completely asymmetric situation is obtained with one s=${1/2}$ component strongly screened by the Kondo effect and the other one almost free to yield indirect magnetism, which shows finally a possible coexistence between a RKKY interaction and a local Kondo effect, as observed in Uranium compounds such as $UPt_3$.Comment: 27 pages, RevTeX, to be published in PR

Nonlinear electrodynamics of p-wave superconductors

We consider the Maxwell-London electrodynamics of three dimensional superconductors in p-wave pairing states with nodal points or lines in the energy gap. The current-velocity relation is then nonlinear in the applied field, cubic for point nodes and quadratic for lines. We obtain explicit angular and depth dependent expressions for measurable quantities such as the transverse magnetic moment, and associated torque. These dependences are different for point and line nodes and can be used to distinguish between different order parameters. We discuss the experimental feasibility of this method, and bring forth its advantages, as well as limitations that might be present.Comment: Fourteen pages RevTex plus four postscript figure

Nonlinear Magneto-Optical Response of ss- and dd-Wave Superconductors

The nonlinear magneto-optical response of $s$- and $d$-wave superconductors is discussed. We carry out the symmetry analysis of the nonlinear magneto-optical susceptibility in the superconducting state. Due to the surface sensitivity of the nonlinear optical response for systems with bulk inversion symmetry, we perform a group theoretical classification of the superconducting order parameter close to a surface. For the first time, the mixing of singlet and triplet pairing states induced by spin-orbit coupling is systematically taken into account. We show that the interference of singlet and triplet pairing states leads to an observable contribution of the nonlinear magneto-optical Kerr effect. This effect is not only sensitive to the anisotropy of the gap function but also to the symmetry itself. In view of the current discussion of the order parameter symmetry of High-T$_c$ superconductors, results for a tetragonal system with bulk singlet pairing for various pairing symmetries are discussed.Comment: 21 pages (REVTeX) with 8 figures (Postscript

Pinning-induced transition to disordered vortex phase in layered superconductors

Destruction of the vortex lattice by random point pinning is considered as a mechanism of the ``second peak'' transition observed experimentally in weakly coupled layered high temperature superconductors. The transition field separating the topologically ordered quasilattice from the amorphous vortex configuration is strongly influenced by the layered structure and by the nonlocal nature of the vortex tilt energy due to the magnetic interlayer coupling. We found three different regimes of transition depending on the relative strength of the Josephson and magnetic couplings. The regimes can be distinguished by the dependence of the transition fieldComment: 8 pages, 3 Postscript figures. Accepted to Phys. Rev.B. (regular article

Ground State Vortex Lattice Structures in d-wave Superconductors

We show in a realistic $d_{x^{2}-y^{2}}$ symmetry gap model for a cuprate superconductor that the clean vortex lattice has discontinuous structural transitions (at and near T=0), as a function of the magnetic field $B$ along the c-axis. The transitions arise from the singular nonlocal and anisotropic susceptibility of the $d_{x^{2}-y^{2}}$ superconductor to the perturbation caused by supercurrents associated with vortices. The susceptibility, due to virtual Dirac quasiparticle-hole excitation, is calculated carefully, and leads to a ground state transition for the triangular lattice from an orientation along one of the crystal axis to one at 45$^o$ to them, i.e, along the gap zero direction. The field scale is seen to be 5 Tesla $\sim (\Delta_{0}/ta)^{2}\Phi_{0}$, where $\Delta_{0}$ is the gap maximum, $t$ is the nearest neighbour hopping, $a$ is the lattice constant, and $\Phi_{0}$ is the flux quantum. At much higher fields ($\sim 28T$) there is a discontinuous transition to a centred square structure. The source of the differences from existing calculations, and experimental observability are discussed, the latter especially in view of the very small (a few degrees $K$ per vortex) differences in the ground state energy.Comment: To be published in Phys. Rev.

Learning Mechanics and Game Mechanics Under the Perspective of Self-Determination Theory to Foster Motivation in Digital Game Based Learning

Background: Using digital games for educational purposes has been associated with higher levels of motivation among learners of different educational levels. However, the underlying psychological factors involved in digital game based learning (DGBL) have been rarely analyzed considering self-determination theory (SDT, Ryan \& Deci, 2000b); the relation of SDT with the flow experience (Csikszentmihalyi, 1990) has neither been evaluated in the context of DGBL