Forward jet-like event spin-dependent properties in polarized p+p collisions at s\sqrt{s}=200 GeV

The STAR collaboration has reported precision measurements on the transverse single spin asymmetries for the production of forward $\pi^0$ mesons from polarized proton collisions at $\sqrt{s} =\,$200 GeV. To disentangle the contributions to forward asymmetries, one has to look beyond inclusive $\pi^0$ production to the production of forward jets or direct photons. Present forward detector capabilities are not well matched to the complete reconstruction of forward jets, but do have sufficient acceptance for "jet-like" events. "Jet-like" events are the clustered response of an electromagnetic calorimeter that is primarily sensitive to incident photons, electrons and positrons. During the RHIC running in the year 2006, STAR with the Forward Pion Detector (FPD++) in place collected 6.8 pb$^{-1}$ of data with an average polarization of 60%. FPD++ was a modular detector prototype of the Forward Meson Spectrometer (FMS) that consisted of two detectors placed symmetrically with respect to the beam line at a distance of 7.4 m from the interaction point. Readout of the FPD++ was triggered when the sum of energies in the central module of the calorimeter used for $\pi^0$ measurements was larger than a threshold. This trigger minimizes the bias for "jet-like" events, making it appropriate to disentangling contributions to the forward transverse spin asymmetries. We report on the status of the analysis.Comment: 5 pages, 6 figures, SPIN10 conference (Juelich, Germany, 2010

Amphibian decline and their protection in Croatia

Vodozemci su među najugroženijim životinjama na Zemlji. Oko jedna trećina danas poznatih vrsta ozbiljno je ugrožena i vrlo je moguće da neće preživjeti ovo stoljeće. U zadnjih 30 godina nestalo je oko 200 vrsta, od kojih su mnoge bile jedinstvene. Premda je u istraživanje ove zabrinjavajuće pojave uložen popriličan trud, vrijeme i novac, još uvijek postoji mnogo više pitanja nego odgovora u vezi nestajanja vodozemaca. Čini se da je za postizanje rezultata potrebno dugotrajno, sustavno i široko praćenje stanja populacija vodozemaca. Od lokalnih uzročnika nestajanja vodozemaca svakako je značajan nestanak, promjena i fragmentacija staništa, unošenje novih predatora i kompetitora, zagađenje i pretjerano iskorištavanje u komercijalne svrhe. U globalne uzročnike ubrajaju se povišenje temperature uslijed globalnog zagrijavanja, kao i druge posljedice istog, kao npr. regionalne promjene u vodnom režimu (posebice povećana učestalost suša), isušivanje tla, produženje sušnih razdoblja, i sve veća varijabilnost količine oborina. Kao uzroci navode se još kisele kiše, deforestacija i pojačano UV-B zračenje. Svi ovi čimbenici mogu djelovati direktno izazivajući smrt ili indirektno uzrokujući stres. U Hrvatskoj ne postoji sustavno praćenje populacija vodozemaca. Trebalo bi organizirati široku mrežu aktivnosti raznih lokalnih udruga, koje bi koordinirala ekipa stručnjaka. Time bi se dobili vrijedni podaci o stanju populacija u Hrvatskoj. U ovom trenutku ne možemo sa sigurnošću tvrditi da nestajanja nema, dok u svakom slučaju određeni rizični čimbenici postoje.Amphibians belong to one of the most critically endangered group of animals on planet Earth. About one third of the species are seriously in danger and it is possible that they will not survive this century. In the last 30 years about 200 species have disappeared and some of them were unique. A hard work, time and money were invested in the research of causes of amphibian decline but there are still more questions then the answers. It seems that we need long and systematic monitoring over populations of amphibians so they can provide some results. Local factors that cause disappearance of amphibians are: changed or lost habitat, its fragmentation, import of the predators and competitors, pollution and huge exploitation. Global factors are: temperature rising as a consequence of global warming, and other causes such as regional changes in water heights (especially rising frequency of dry periods), soil melioration and variability of rain seasons. There are also acid rains, deforestation and high UV – B radiation. All of these factors can act directly causing death or indirectly causing stress. In Croatia does not exist systematic monitoring over populations of amphibians. We should organise activities of local groups (such as monitoring), who would be under surveillance of scientist. In this way we can get important information about populations that live here. In this moment we can not discuss about amphibian decline because there is no data evidence, but there are some factors of risk

Variants of ring rolling methods

Predložená práca vypracovaná v rámci bakalárskeho štúdia B23390-00 Strojní inženýrství sa zaoberá technológiou valcovania prstencov. V rešerši sú popísané princípy technológie valcovania prstencov, prehľad tvarových skupín vyrábaných dielcov za tepla a za studena a prehľad nástrojov a strojov používaných v rámci technológie.The submitted work developed within the bachelor study B23390-00 Mechanical engineering deals with technology of ring rolling. Principles of the technology of ring rolling, list of various shapes produced by hot and cold ring rolling and summary of machines and tools used within this technology are described in this recherché.

DNA-polymerase: mechanisms of replication fidelity

DNA-polimeraze su kompleksni, multikomponentni enzimi koji kataliziraju reakciju sinteze DNA. One postižu brzine sinteze koje su sukladne fiziološkoj brzini rasta, a uz to postižu relativno visoke stope vjernosti replikacije. Cilj ovog seminara je bio objasniti kako DNA-polimeraze to postižu. Pokazalo se da ovi enzimi to postižu korištenjem različitih domena za polimerizaciju i korekciju, s antagonističkim katalitičkim funkcijama. Možemo izvući općeniti zaključak da su za visoku vjernost sinteze DNA odgovorni komplementarnost baza, inducirano pristajanje i 3’-5’ egzonukleazna aktivnost. Prvo, imamo početnu selekciju pravilnih parova baza na temelju geometrije. Zatim, vezanjem odgovarajućeg nukleotida nastaje konformacijska promjena koja pruža steričku provjeru geometrije para baza, nakon čega slijedi brza ugradnja nukleotida u rastući polimer. Ugradnjom krive baze dolazi do inhibicije ove konformacijske promjene kao i inhibicije polimerizacije, čime se omogućuje prebacivanje novosintetiziranog lanca u mjesto za popravljanje gdje se 3’-5’ egzonukleaznom aktivnošću odstranjuje krivo ugrađena baza. Sveukupna vjernost replikacije dolazi i do vrijednosti od jedne greške na 1010 ugrađenih nukleotida, što je kombinacija selektivnosti u polimerizaciji (105-106) i korektivnoj aktivnosti (103-106). Također, uz polimeraze koje postižu visoku vjernost replikacije imamo i one koje nisu toliko vjerne, ali ni specifične, te su stoga pogodne za replikaciju oštećenih molekula DNA, koju ne mogu provoditi obične DNA-polimeraze. Potrebno je napomenuti da nijedna DNA-polimeraza ne djeluje sama. Replikacija DNA uključuje ogromne komplekse DNA-polimeraza sa mnoštvom pomoćnih proteina koji na razne načine utječu na njenu procesivnost i efikasnost. Budući da kompleksnost polimerizacijskih reakcija in vitro nije ni približna onima u stanici, preostaju nam mnoga istraživanja koja će nam dati jasniju i detaljniju sliku kako zapravo stanice repliciraju svoj genom.DNA-polymerases are complex, multidomain enzymes that catalyze reactions of DNA replication. They achieve rates of synthesis that support physiological growth rates and yet preserve relatively high fidelity. The goal of this seminar was to explain how do they manage to do that. It has been shown that they achieve that by using distinct domains for polymerization and for proofreading, with antagonistic catalytic functions. We can draw general conclusion that high fidelity synthesis of DNA are driven by several factors: complementary base pairing, induced fit and 3’-5’ exonuclease activity. Firsty, initial selection of correct base pair is achieved on the basis of geometry. Then, binding of the correct nucleotide induces conformational change, which provides steric check for the proper base pair geometry, followed by a rapid incorporation of nucleotide into the growing polymer. Mismatch inhibits this conformational change as well as polymerization, allowing the transfer of newly synthesized chain into editing site, where the incorrect base is removed by 3’-5’ exonuclease. The overall fidelity approaches one error in 1010 by a combination of selectivity in polymerization (105-106) and in proofreading (103-104). Also, beside the high fidelity polymerases there are low fidelity ones, which are not so specific, and are therefore suitable for the replication of damaged DNA molecules, which can not be carried out by normal DNA-polymerases. It is necessary to note that no DNA-polymerase works alone. DNA replication involves huge complexes of DNA-polymerases with multitude accessory proteins, which in many ways affect its processivity and efficiency. Since the complexity of polymerization reactions in vitro does not even approximate those in the cell, many research remains to be done that will give us a clearer and more detailed picture of how do cells replicate their own genome