Domain enhanced interlayer coupling in ferroelectric/paraelectric superlattices

We investigate the ferroelectric phase transition and domain formation in a periodic superlattice consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. We find that the polarization domains formed in the different FE layers can interact with each other via the PE layers. By coupling the electrostatic equations with those obtained by minimizing the Ginzburg-Landau functional we calculate the critical temperature of transition Tc as a function of the FE/PE superlattice wavelength and quantitatively explain the recent experimental observation of a thickness dependence of the ferroelectric transition temperature in KTaO3/KNbO3 strained-layer superlattices.Comment: Latest version as was published in PR

HALL EFFECT AND MAGNETORESISTANCE IN THE HEAVY-ELECTRON COMPOUND UCu5 AT AMBIENT PRESSURE AND 1 GPa

Magnetoresistance and Hall effect measurements on a polycrystalline sample of UCU5 have been made in magnetic fields up to 20 T and at temperatures as low as 0.3 K. The results give evidence for a magnetic field induced high resistive state and a magnetic transition in high fields. © 1987

Parasites and immunotherapy: with or against?

Immunotherapy is a sort of therapy in which antibody or antigen administrates to the patient in order to treat or reduce the severity of complications of disease. This kind of treatment practiced in a wide variety of diseases including infectious diseases, autoimmune disorders, cancers and allergy. Successful and unsuccessful immunotherapeutic strategies have been practiced in variety of parasitic infections. On the other hand parasites or parasite antigens have also been considered for immunotherapy against other diseases such as cancer, asthma and multiple sclerosis. In this paper immunotherapy against common parasitic infections, and also immunotherapy of cancer, asthma and multiple sclerosis with parasites or parasite antigens have been reviewe

Safe way to school

Podróż do szkoły jest codziennością każdego dziecka. Kilkulatkowie są odwożeni przez rodziców, starsze dzieci już same docierają do szkoły. [1] Różne sposoby przebycia drogi do szkoły generują liczne niebezpieczeństwa i problemy. Zakorkowane ulice nieopodal szkoły, nieostrożne przechodzenie dzieci przez jezdnie, brak wyrozumiałości kierowców to niektóre z nich. Projekt skupia się na próbie rozwiązania tych kłopotliwych sytuacji. Podstawą do zlokalizowania najbardziej niebezpiecznych miejsc były ankiety przeprowadzone w szkole. Jej wynik stał się fundamentem do dalszych działań. Na podstawie badań wybrano miejsca, które wymagają naprawy, innej organizacji. W pracy przedstawiono propozycję zmian z zakresu bezpieczeństwa ruchu drogowego jak i zmiany infrastrukturalne tworzące przyjazną pieszym bezkolizyjną infrastrukturę drogową.Traveling to school is the everyday routine of every child. Several-year-olds are brought to school by their parents, older children are getting to school themselves. Different ways of going to school generate many dangers and problems. Overcrowded streets near the school, careless children crossing the road, lack of understanding of the drivers are some of them. The project focuses on trying to solve these embarrassing situations. School surveys were the basis for finding the most dangerous places. Its result become the foundation for further action. Based on the research, you have selected locations that require repair, another organization. The article presents changes in road safety and changes in infrastructure that make pedestrian-friendly road infrastructure without collisions

Couches minces supraconductrices à haute température critique : preparation in-situ de films orientés de YBa2_2CU3_3O7−X_{7-X} par depôt plasma

Superconducting thin-films of YBa$_2$CU$_3$O$_{7-X}$ material have been grown in situ by single target d.c. sputtering, Single-crystal (100)MgO, (100)SrTiO$_3$ and (110)SrTiO$_3$ substrates were heated between 600 and 700 $^{\circ}$C and the film orientation has been studied as a function of substrate temperature. X-ray diffraction photographs, taken in a Weissenberg camera, were used to study the in-plane orientation of the films and to determine the epitaxial growth relations with the substrates. Films displayed only textured growth near 650 $^{\circ}$C and epitaxial growth near 700 $^{\circ}$C. These thin-films have been measured by resistive and inductive techniques. Best samples, obtained on SrTiO$_3$, exibit $T_{\rm c}$ onsets between 87 and 89 K, $T_{\rm c}$ ($R = 0$) between 85 and 87 K and critical current densities of about 10$^6$ A cm$^{-2}$ at 77 K. The transition width of these samples, as determined from the inductive response, is less than 1 K. We observed a clear correlation between the width of the a.c. inductive transition and the film quality and used this sensitive method for deposition-parameter optimization.Des couches minces du matériau supraconducteur YBa$_2$CU$_3$O$_{7-X}$ ont été préparées in situ par pulvérisation cathodique diode continue monocible sur des substrats monocristallins (100)MgO, (100)SrTiO$_3$ et (110)SrTiO$_3$ chauffés entre 600 et 700 $^{\circ}$C. L'orientation des films obtenus a été étudiée en fonction de la température du substrat. L'étude aux rayons X par application de la méthode du cristal tournant a permis d'observer le passage d'une croissance texturée à une croissance épitaxiale vers 700 $^{\circ}$C et de déterminer les relations d'épitaxie avec les divers substrats. Les films ont été caractérisés par mesures résistives et inductives. Les meilleurs échantillons, déposés sur SrTiO$_3$, présentent des températures de début de transition résistive comprises entre 87 à 89 K, des températures de fin de transition ($R = 0$) de 85 à 87 K et des densités de courant critique (77 K) de l'ordre de 10$^6$ A cm$^{-2}$. Les largeurs de transition, déterminées par la méthode inductive, sont inférieures à 1 K. La réponse inductive est d'ailleurs fortement corrélée à la qualité des films et constitue une méthode de choix pour déterminer les conditions optimales de préparation

Hall effect and magnetoresistance in the heavy-electron compound UCu5 at ambient pressure and 1 GPa

Magnetoresistance and Hall effect measurements on a polycrystalline sample of UCU5 have been made in magnetic fields up to 20 T and at temperatures as low as 0.3 K. The results give evidence for a magnetic field induced high resistive state and a magnetic transition in high fields. © 1987