Primordial Magnetic Field from Gravitationally Coupled Electrodynamics in Bouncing Scenario

We in this paper study the generation of primordial magnetic field (PMF) in the non-singular bouncing scenario, through the coupling of the electromagnetic field to gravity. We adopt an electrodynamic model with a coupling coefficient as a function of the scale factor $a$, i.e. $f=1+(a/a_\star)^{-n}$, with $a_\star$ and $n>0$ being constants. The result implies that in this mechanism, the power spectrum of PMF today is always blue tilted on large scales from $1$ Mpc to the Hubble length, and the observational constraints favor the ekpyrotic-bounce scenario. Furthermore, the back reaction of the energy density of PMF at the bouncing point yields theoretical constraints on the bouncing model

Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

International audienceWe have used ion irradiation to tune switching field and switching field distribution ͑SFD͒ in polycrystalline Co/Pd multilayer-based bit pattern media. Light He + ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity ͑H C ͒ but also to a strong broadening of the normalized SFD/ H C ͑in percentage͒, since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays. Today a major research effort in magnetism is targeted toward achieving ultrahigh density data storage with nano-scale magnets. Spin-transfer magnetic random access memory ͑spin-RAM͒ and bit patterned media ͑BPM͒ technologies are currently part of the most promising media. The implementation of both of these technologies relies on achieving in-detail physical understanding and control of the magnetization reversal mechanism in each nanoscopic individual bit to ensure reproducibility of the bit properties in order to avoid write errors. Perpendicular magnetic anisotropy ͑PMA͒ materials, such as polycrystalline Co/Pd, Co/Pt, and Co/Ni multilayers, are believed to be promising materials for both spin-RAM and BPM applications. 1–4 Indeed, they have a well defined high amplitude uniaxial anisotropy that provides good thermal stability while offering low critical current in spin-transfer devices 2 and tunable switching fields in BPM.

2D InP photonic crystal fabrication process development

We have developed a reliable process to fabricate high quality 2D air-hole and dielectric column InP photonic crystals with a high aspect ratio on a STS production tool using ICP N2+Cl2 plasma. The photonic crystals have a triangular lattice with lattice constant of 400 nm and air-hole and dielectric column radius of 120 nm. Large efforts have been devoted on developing a proper mask. We obtained a perfect, clean and vertical profiled SiNx mask. The next main effort is InP pattern transfer in Cl 2+N2 plasma. Etching selectivity, smooth sidewall and etch profile are directly related to plasma process condition, besides the quality of SiNx mask. We have optimized the N2+Cl2 plasma condition to obtain high aspect ratio, vertical profile and smooth sidewall InP structures. Cylindrical holes (2 micron depth) and rodlike pillars (2.4 micron height) are uniformly fabricated. An aspect ratio of 18 for 100nm trench lines has been obtained. AFM measurement evidences that etched surfaces are smooth. The root mean square roughness of pillar and hole is 0.7 nm and 0.8 nm, respectively. The optical transmission characterization of ridge waveguides has been carried out. Transmission spectrum of 1 micron wide waveguide has been obtained

Optimizing omnidirectional reflection by multilayer mirrors

Periodic layered media can reflect strongly for all incident angles and polarizations in a given frequency range. Quarter-wave stacks at normal incidence are commonplace in the design of such omnidirectional reflectors. We discuss alternative design criteria to optimize these systems.Comment: 9 pages, 6 figures. To be published in J. Opt. A: Pure and Applied Optic

Electromigration studies in amorphous and polycrystalline alloys

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Investigation of carbon anode matertials stability towards various electrolytes in Li-ion cells

Nieustanny rozwój cywilizacji powoduje potrzebę pracy nad przenośnymi urządzeniami elektronicznymi, stanowiąc tym samym impuls do poszukiwań nowych materiałów i badania ich możliwości zastosowania w systemach bateryjnych czy akumulatorach. Rodzina technologii jaką stanowią akumulatory litowo-jonowe przoduje w przenośnych systemach magazynowania energii. Mimo korzyści wynikających z ich zastosowania, ogniwa Li-ion posiadają pewne niedoskonałości, pozostawiając tym samym miejsce na rozwój badań w wielu aspektach ich parametrów pracy. Celem przeprowadzonych badań było określenie wpływu składu zastosowanego elektrolitu na funkcjonowanie ogniw. W ramach pracy dokonano charakterystyki parametrów pracy ogniw litowych przy zastosowaniu różnych ciekłych elektrolitów otrzymanych z wykorzystaniem soli: LiPF6, LiClO4, LiBOB i rozpuszczalników: EC, DMC, DEC, TMS, EMC. Prowadzone badania opierały się na wykorzystaniu w roli jednej z elektrod ogniwa materiału węglowego (aerożelu) bazującego na naturalnej skrobi ziemniaczanej (CAGPS). Zmontowane ogniwa poddano galwanostatycznym testom ładowania-rozładowania półogniw (GCDT). Najlepszą charakterystykę pracy, spośród przetestowanych wykazało ogniwo, w którym elektrolit stanowiła sól LiPF6 w mieszaninie rozpuszczalników EC:DEC:DMC. Obiecujące, choć wymagające dalszych badań wydaje się również zastosowanie w takim ogniwie elektrolitu z wykorzystaniem soli LiClO4 w rozpuszczalnikach EC:DMC.The constant development of civilization causes the need to work on portable electronic devices, which is an impulse to search for new materials and conduct research on their possible use in battery systems. The technology of lithium-ion battery excels in portable energy storage systems. Despite the benefits of their use, Li-ion cells have some imperfections, which is why the research is carried out in many aspects of their working parameters. The aim of the research was to examine the impact of electrolyte composition on the functioning of the cells. As a part of the study, characteristics of the operating parameters of lithium cells, utilizing various liquid electrolytes obtained with the use of salts: LiPF6, LiClO4, LiBOB and solvents: EC, DMC, DEC, TMS, EMC, was performed. The research relied on the employing of carbon material (aerogel) obtained from natural precursor - potato starch (CAGPS) as one of the electrodes. The assembled cells were characterized by galvanostatic charge-discharge tests (GCDT).The best characteristics among the cells tested was shown by the cell in which the electrolyte was LiPF6 salt in the solvent mixture EC:DEC:DMC 1:1:1 by volume. Electrolyte with LiClO4 in the mixture of solvents EC:DMC seems promising, although further research are required

Reliefs discovered in Nidaros cathedral's tower and stone sculpture of Trondelag region in Norway around 1066 - 1153.

Przedmiot niniejszej pracy stanowią cztery wybrane fragmenty rzeźby architektonicznej z płaskorzeźbionymi dekoracjami, wydobyte z murów głównej wieży katedry w Nidaros w roku 1888, podczas jej największej w dziejach restauracji. Jej cel natomiast stanowi wpisanie wskazanej grupy w jak najszerszy zakres kontekstów historycznych i historyczno - artystycznych, co służyć ma próbie rekonstrukcji warunków rozwoju kamiennej rzeźby regionu Trondelag w Norwegii w latach ok. 1066 - 1153. Punktem wyjścia do podjęcia niniejszych rozważań jest założenie istnienia sieci powiązań artystycznych zarówno w wymiarze lokalnym jak i międzynarodowym, w które wpisywało się średniowieczne Nidaros, skutkując rozkwitem kulturowym i artystycznym miasta i regionu, we wskazanym okresie.The subject of this thesis is a group of four chosen stone blocks,decorated with reliefs, excavated from the walls of the main tower of Nidaros cathedral, during it's main restoration works in 1888. The aim for this work is to locate the fragments in the widest possible historical and artistic background, in order to make an attempt to reconstruct the conditions of stone sculpture's development in Trondelag in Norway around 1066 - 1153. What is being assumpted here is existence of an extensive network of artistic relations, both in local and international sense, in which Nidaros was actively participating