Inferring type and scale of noncommutativity from the PTOLEMY experiment

If neutrinos are Dirac particles and their right-handed component can be copiously produced in the early universe, then they could influence a direct observation of the cosmic neutrino background, which, most likely, will come about with the recently proposed PTOLEMY experiment. For the production mechanism of right-handed neutrinos we use a state-of-the-art version of gauge field theory deformed by the spacetime noncommutativity, to disclose by it not only the decoupling temperature for the said neutrino component, but also the otherwise hidden coupling temperature. Considering two relevant processes, the plasmon decay and the neutrino elastic scattering, we study the interplay between the structure of the noncommutativity parameter $\theta^{\mu \nu}$ (type of noncommutativity) and the reheating temperature after inflation to obtain otherwise elusive upper bound on the scale of noncommutativity $\Lambda_{\rm NC}$. If PTOLEMY enhanced capture rate is due to spacetime noncommutativity, we verify that a nontrivial maximum upper bound on $\Lambda_{\rm NC}$ (a way below the Planck scale) emerges for a space-like $\theta^{\mu \nu}$ and sufficiently high reheating temperature.Comment: 6 pagees, 1 figure, version of article to be published in EPJ

Off-axis MgB2 films using an in situ annealing pulsed laser deposition method

Highly smooth and c-axis oriented superconducting MgB2 thin films were prepared by pulsed laser deposition (PLD) with off-axis geometry. The films were deposited on Al2O3-C substrates perpendicularly aligned to a stoichiometric MgB2 target in a 120 mTorr high purity Ar background gas. An in situ annealing was carried out at 650C for 1 min in a 760 Torr Ar atmosphere. Despite the short annealing time, an x-ray theta-2 theta scan shows fairly good crystallization, according to the clear c-axis oriented peaks for the films. Both atomic force microscopy and the x-ray diffraction results indicate that the crystallite size is less than 50nm. The root mean square roughness of our off-axis film is ~4 nm in a 5x5 square micron area. The Tc onset value of the best off-axis film reaches 33.1 K with a narrow transition width of 0.9 K. The films showed no anisotropy in Hc2-T curves when parallel and perpendicular fields were applied. The slope of Hc2-T curves in low field regime is 1 T/K, which is among the highest reported values.Comment: 7 pages 7 figure

Soil compaction in timber skidding in winter conditions

The research of soil compaction in timber skidding was carried out on two skid trails of uniform slope –15%and 30 %. The degree of soil compaction is shown by changes of water-air soil characteristics of the skid trail after a certain number of passes of a loaded skidder and by comparison between these values and the characteristics of untreaded soil during research. The research was carried out in winter conditions at low air and soil temperatures and with the research site covered with snow. Multiple passes of a loaded skidder affect the degree of soil compaction. The result of soil compaction is the decrease of momentary moisture content, porosity and soil water capacity, as well as the increase of native bulk density. Soil compaction is higher if the soil is not frozen. Due to low air temperatures and disappearance of snow from wheel ruts during skidding, the rut soil gets frozen more easily during the night than the untreaded soil. Soil compaction during the day does not cause squeezing out of water from soil micropores and consequently its freezing enlarges the volume of micropores and increases soil porosity and soil water capacity and decreases its native bulk density

Razvoj robotskog stereotaktičkog okvira za primjenu u neurokirurgiji

Ovim radom prikazan je razvoj robotiziranog stereotaktičkog okvira za primjenu u neurokirurgiji. Razvoj medicinske tehnologije usmjeren je ka većoj točnosti izvođenja zahvata, manjoj traumi pacijenta, bržem oporavaku te boljim ukupnim kliničkim rezultatima. Robotika i razvoj računarskih znanosti postavljeni su kao logičan odgovor na pitanje unapređenja medicinskih zahvata. Početak razvoja sustava započeo je analizom standardne medicinske opreme za stereotaktičku neurokirurgiju, točnije Leksellovog stereotaktičkog uređaja. U radu je prikazan razvoj koncepta robotiziranog stereotaktičkog uređaja, oblikovanje robotiziranog stereotaktičkog okvira te je provedena analiza razvijenog sustava. Sadržaj diplomskog rada može se podijeliti u nekoliko cjelina. Prvu cjelinu možemo promatrati kao uvođenje u područje robotike i neurokirurgije. Prikazan je razvoj tehnologije u medicini i primjer trenutačnih dosega u razvoju neurokirurških robotskih sustava. Druga cjelina je razvoj koncepta stereotaktičkog uređaja za primjenu u neurokirurgiji. Prikazana je kinematska struktura robota i nekoliko kinematskih koncepta uređaja. Proces koncipiranja završava vrednovanjem i odabirom optimalnog rješenja za konstrukcijsku razradu. Za odabrani koncept potrebno je razviti robotizirani stereotaktički okvir koji predstavlja novu cjelinu diplomskog rada. Konstruiranje robotiziranog stereotaktičkog okvira predstavlja cjelinu u kojoj su odabrane izvedbe pojedinih osi te provedeni proračuni elemenata. Nakon odabranih kombinacija elemenata pogona osi robota slijedila je faza skiciranja i razrade sustava. Za odabrane elemente i princip rada oblikovan je sustav za koji je priložen opis . Nakon oblikovanja sustava slijedila je faza analize točnosti pozicioniranja, prikaza karakteristika enkodera, te opisa sigurnosnih karakteristika sustava. Zadnja cjelina je zaključak u kojemu su opisani doprinosi ovog rada i nabrojeni daljnji smjerovi razvoja sustava