Hydrogen and oxygen isotope behaviors during variable degrees of upper mantle melting: Example from the basaltic glasses from Macquarie Island

We present measurements of hydrogen and oxygen isotopes in MORB glasses from Macquarie Island (SW. Pacific Ocean) coupled with determination of bulk H2O content by two independent techniques: total dehydration and FTIR. The incompatible trace elements in these glasses vary by a factor of 12 to 17, with K2O varying from 0.1 to 1.7 wt.%; these ranges reflect a variable degree of closed-system mantle melting, estimated from 1 to 15%. Water concentrations determined by the two techniques match well, yielding a range from 0.25 to 1.49 wt.% which correlates positively with all of the measured incompatible trace elements, suggesting that water is un-degassed, and behaves conservatively during mantle melting. Also, the agreement between the FTIR-determined and extracted water contents gives us confidence that the measured isotopic values of hydrogen reflect that of the mantle. Comparison of the range of water content with that of other incompatible trace elements allows estimation of the water partition coefficient in lherzolite, 0.0208 (ranging from 0.017 to 0.023), and the water content in the source, 386 ppm (ranging from 370 to 440 ppm). We observe a fairly narrow range in delta D and delta O-18 values of -75.5 +/- 4.5 parts per thousand and 5.50 +/- 0 .05 parts per thousand respectively, that can be explained by partial melting of normal lherzolitic mantle. The measured delta D and delta O-18 values of Macquarie Island glasses that range from nepheline- to hypersthene-normative, and from MORB to EMORB in composition, are identical to those in average global MORB. The observed lack of variation of delta D and delta O-18 with 1 to 15% degree of mantle melting is consistent with a bulk melting model of delta D and delta O-18 fractionation, in which water is rapidly scavenged into the first partial melt. The narrow ranges of delta D and delta O-18 in normal mantle are mostly due to the buffering effect of clino- and orthopyroxenes in the residual assemblage; additionally, fast ``wet'' diffusion of oxygen and hydrogen isotopes through the melting regions may further smooth isotopic differences. (C) 2012 Elsevier B.V. All rights reserved.

Aplicaciones de la Teor��a de Matrices en Matem��tica Discreta

Se describen algunas aplicaciones de la teor��a de matrices a diversos temas pertenecientes al��mbito de la matem\'atica discreta.

Oxygen adsorption on Cu(510)

T��ss�� ty��ss�� on tutkittu kuparin (510)-askelpinnan reaktiivisuutta k��ytt��en apuna kvanttimekaanisia ab initio laskentamenetelmi��. Tutkimus on toteutettu laskemalla happiatomin adsorptioenergia ja tilatiheys erilaisissa potentiaalisissa adsorptiopaikoissa pinnalla. My��s happimolekyylin adsorptiota ja hajoamista ontarkasteltu laskemalla pintaa l��hestyv��lle molekyylille potentiaalienergiapintoja. Energiapintojen tuloksia on my��s t��ydennetty kvanttimekaanisilla molekyylidynamiikkalaskuilla. Metallisia askelpintoja pidet����n yleisesti sileit�� pintoja reaktiivisempina happea kohtaan, johtuen askeleen reunan pienent��v��st�� vaikutuksesta molekyylin hajoamisen tiell�� olevaan energiavaliin. On kuitenkin olemassa my��s tuloksia, jotka osoittavat hapen tarttumisprosessin olevan hallitseva juuri terassialueella, askeleen reunan sijasta. T��ss�� ty��ss�� on todettu hapen adsorboituvan Cu(510)-pinnalla tehokkaimmin juuri terassilla olevaan hollow-paikkaan. My��s adsorptioenergiat ovat t��ll�� pinnalla pienempi�� kuin sile��ll�� (100)-pinnalla. Potentiaalienergiapintojen perusteella Cu(510)-pinnan todetaan my��s olevan v��hemm��n reaktiivinen kuin askelpintojen yleisesti odotetaan olevan, vaikka askeleen reunan todetaankin pienent��v��n happiatominhajoamisen esteen�� olevaa energiavallia.

Effect of antifoams on oxygen mass transfer in pulp and paper mill effluents

Vaahdonestoaineiden haitallinen vaikutus hapen liukenemisnopeuteen biologisen puhdistamon j��tevesiss�� on yleisesti tunnettua. Aineiden eri vaikutusmekanismien takia on silti vaikea etuk��teen arvioida, miten ja kuinka paljon aineensiirto muuttuu. Ty��n tavoitteena oli saada tietoa vaahdonestoaineiden ja muiden pinta-aktiivisten aineiden vaikutuksesta kuplakokoon, kaasun tilavuusosuuteen ja kaasu-neste aineensiirtoon. Ty��n teoriaosassa on kuvailtu vaahdon muodostumiseen vaikuttavia tekij��it�� sek�� eri vaahdonestoaineiden vaikutusmekanismeja sellu- ja paperitehtaan j��tevedess��. Edelleen on esitetty useita hapen siirtoa est��vi�� ja parantavia aineita. Ty��n kokeellisessa osassa tutkittiin kahdenkymmenenviiden eri pinta-aktiivisen aineen vaikutusta hapen liukenemisnopeuteen yksivaiheisessa kuplakolonnissa. Kokeet tehtiin kahdella pitoisuudella, kahdella eri kaasunjakolaitteella ja kolmella eri kaasun tyhj��putkinopeudella. Aineensiirtokokeiden rinnalla tutkittiin j��tevesien laatu- ja fysikaalisiaominaisuuksia, niiden vaikutusta hapen liukenemisnopeuteen sek�� testattavien koeaineiden vaikutusta fysikaalisin ominaisuuksiin. Kokeet osoittavat ett�� pinta-aktiivisten aineiden vaikutus hapen aineensiirtoon vaihtelee riippuen kaasunjakolaitteesta ja aineen pitoisuuksista. Testatuista vaahdonestonaineista pienin negatiivinen vaikutus oli aineella AT 35 ja positiivinen vaikutustodettiin olevan vaahdonestoaineiden komponenteilla: P2, S1, F4 ja T9.

Oxygen adsorption on Cu(211) and structurally and chemically modified Cu(100)

Kuparipinnan hapettuminen on viimevuosina ollut suosittu tutkimuskohde materiaalitieteiss�� kuparin laajan teollisuusk��yt��n vuoksi. Teollisuussovellusten, kuten suojaavien pintaoksidien kehitt��minen vaatii kuitenkin syv��llist�� tuntemusta hapettumisprosessista ja toisaalta my��s normaaliolosuhteissa materiaalissa esiintyvien hilavirheiden vaikutuksesta siihen. T��ss�� ty��ss�� keskityt����nkin tutkimaan juuri niit�� mekanismeja, joilla erilaiset pintavirheet ja porrastettu pintarakenne vaikuttavathapen adsorptioprosessiin kuparipinnalla. Tutkimus on tehty k��ytt��m��ll�� laskennallisia menetelmi�� sek�� VASP- ja SIESTA-ohjelmistoja. Ty��ss��tutkittiin kemiallisia ja rakenteellisia virheit�� Cu(100)-pinnalla, joka on reaktiivisin matalanMillerin indeksin pinta ja porrastetun pinnan tutkimuksessa k��ytettiin Cu(211)-pintaa, joka puolestaan on yksinkertainen, stabiili ja aiemmissa tutkimuksissa usein k��ytetty pintarakenne. Ty��ss�� tutkitut hilavirheet, adatomit, v��hent��v��t molekyylin dissosiaatiota kuparipinnalla, kun taas vakanssit toimivat dissosiaation keskuksina. Kemiallisena ep��puhtautena k��ytetty hopeakerros ei est�� kuparin hapettumista, sill�� happi aiheuttaa mielenkiintoisen segregaatioilmi��n, jossa hopeaty��ntyy syvemm��lle pinnassa j��tt��en kuparipinnan suojaamattomaksi. Porrastetulla pinnalla (100)-hollow on todenn��k��isin paikka molekyylin dissosiaatiolle, kun taas portaan bridge-paikka on suotuisin molekulaariselle adsorptiolle. Lis��ksi kuparin steppipinnan todettiin olevan reaktiivisempi kuin tasaiset kuparipinnat.

The effect of oxygen delignification on fiber properties in kraft pulp production - a review

Fiber damages comprise fiber deformations, characterized as fiber curl, kink, dislocations and strength losses as well as some yet unidentified factors. This recently discovered phenomenon is especially evident in mill scale kraftpulps. Laboratory produced pulps tend to have less damages and superior strength properties compared to those produced in pulp mills. Generally fiber damages pose a problem in the production of reinforcement pulp because they tend to decrease the ability of fibers to transmit load. Previous studies on fiber damage have shown that most of the fiber damages occur during brown stock processing starting from cooking and discharging. This literature review gives an overall picture on fiber damages occurring during softwood kraft pulp production with an emphasis on the oxygen delignification stage. In addition the oxygen delignification stage itself is described in more detailed extent in order to understand the mechanisms behind the delignification and fiber damaging effect. The literature available on this subject is unfortunately quite contradictory and implicates a lotof different terms. Only a few studies have been published which help to understand the nature of fiber damages. For that reason the knowledge presented in this work is not only based on previous studies but also on research scientist and mill staff interviews.

Identification of carotenoids using mass spectrometry

The present review compiles positive MS fragmentation data of selected carotenoids obtained using various ionization techniques and matrices. In addition, new experimental data from the analysis of carotenoids in transgenic maize and rice callus are provided. Several carotenes and oxygen-functionalized carotenoids containing epoxy, hydroxyl, and ketone groups were ionized by atmospheric pressure chemical ionization (APCI)-tandem mass spectrometry (MS/MS) in positive ion mode. Thus, on the basis of the information obtained from the literature and our own experiments, we identified characteristic carotenoid ions that can be associated to functional groups in the structures of these compounds. In addition, pigments with a very similar structure were differentiated through comparison of the intensities of their fragments. The data provide a basis for the structural elucidation of carotenoids by mass spectrometry (MS).

Technical Note: Dissolved organic matter fluorescence a finite mixture approach to deconvolve excitation-emission matrices

The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves individual EEMs is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder-Mead optimisation algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. The EEMs of a simple artificial mixture of fluorophores and DOM samples collected in a Mediterranean river are used to describe the model application and to illustrate a strategy that optimises the search for the optimal output.

TGF-�� dependent regulation of oxygen radicals during transdifferentiation of activated hepatic stellate cells to myofibroblastoid cells

Background: The activation of hepatic stellate cells (HSCs) plays a pivotal role during liver injury because the resulting myofibroblasts (MFBs) are mainly responsible for connective tissue re-assembly. MFBs represent therefore cellular targets for anti-fibrotic therapy. In this study, we employed activated HSCs, termed M1-4HSCs, whose transdifferentiation to myofibroblastoid cells (named M-HTs) depends on transforming growth factor (TGF)-��. We analyzed the oxidative stress induced by TGF-�� and examined cellular defense mechanisms upon transdifferentiation of HSCs to M-HTs. Results: We found reactive oxygen species (ROS) significantly upregulated in M1-4HSCs within 72 hours of TGF-�� administration. In contrast, M-HTs harbored lower intracellular ROS content than M1-4HSCs, despite of elevated NADPH oxidase activity. These observations indicated an upregulation of cellular defense mechanisms in order to protect cells from harmful consequences caused by oxidative stress. In line with this hypothesis, superoxide dismutase activation provided the resistance to augmented radical production in M-HTs, and glutathione rather than catalase was responsible for intracellular hydrogen peroxide removal. Finally, the TGF-��/NADPH oxidase mediated ROS production correlated with the upregulation of AP-1 as well as platelet-derived growth factor receptor subunits, which points to important contributions in establishing antioxidant defense. Conclusion: The data provide evidence that TGF-�� induces NADPH oxidase activity which causes radical production upon the transdifferentiation of activated HSCs to M-HTs. Myofibroblastoid cells are equipped with high levels of superoxide dismutase activity as well as glutathione to counterbalance NADPH oxidase dependent oxidative stress and to avoid cellular damage.

Anomalous optical and electrical recovery process of photoquenched EL2 defect produced by oxygen and boron ion implantation in gallium arsenide

The optical and electrical recovery processes of the metastable state of the EL2 defect artificially created in n���type GaAs by boron or oxygen implantation are analyzed at 80 K using optical isothermal transient spectroscopy. In both cases, we have found an inhibition of the electrical recovery and the existence of an optical recovery in the range 1.1-1.4 eV, competing with the photoquenching effect. The similar results obtained with both elements and the different behavior observed in comparison with the native EL2 defect has been related to the network damage produced by the implantation process. From the different behavior with the technological process, it can be deduced that the electrical and optical anomalies have a different origin. The electrical inhibition is due to the existence of an interaction between the EL2 defect and other implantation���created defects. However, the optical recovery seems to be related to a change in the microscopic metastable state configuration involving the presence of vacancies

Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine rhythmites

Biogeochemical cycles and sedimentary records in lakes are related to climate controls on hydrology and catchment processes. Changes in the isotopic imposition of the diatom frustules (�� 18 O diatom and �� 13 C diatom ) in lacustrine sediments can be used to reconstruct palaeoclimatic and palaeoenvironmental changes. The Lago Chungar�� (Andean Altiplano, 18��15 ��� S, 69��10 ��� W, 4520 masl) diatomaceous laminated sediments are made up of white and green multiannual rhythmites. White laminae were formed during short-term diatom super-blooms, and are composed almost exclusively of large-sized Cyclostephanos andinus.These diatoms bloom during mixing events when recycled nutrients from the bottom waters are brought to the surface and/or when nutrients are introduced from the catchment during periods of strong runoff. Conversely, the green laminae are thought to have been deposited over several years and are composed of a mixture of diatoms (mainly smaller valves of C. andinus and Discostella stelligera ) and organic matter. These green laminae reflect the lake's hydrological recovery from a status favouring the diatom super-blooms (white laminae) towards baseline conditions. �� 18 O diatom and �� 13 C diatom from 11,990 to 11,530 cal years BP allow us to reconstruct shifts in the precipitation/evaporation ratio and changes in the lake water dissolved carbon concentration, respectively. �� 18 O diatom values indicate that white laminae formation occurred mainly during low lake level stages, whereas green laminae formation generally occurred during high lake level stages. The isotope and chronostratigraphical data together suggest that white laminae deposition is caused by extraordinary environmental events. El Ni��o-Southern Oscillation and changes in solar activity are the most likely climate forcing mechanisms that could trigger such events, favouring hydrological changes at interannual-to-decadal scale. This study demonstrates the potential for laminated lake sediments to document extreme pluriannual events.

Oxygen adsorption on clean and oxygen precovered Cu(100)

Kuparipinnan hapettumisen alkuvaiheet ovat viel�� nykyisin tutkijoille ep��selvi��. Kuitenkin, jotta hapettumisprosessia voitaisiin s����dell��, on sangen t��rke���� ymm��rt���� mist�� varsinainen hapettuminen l��htee liikkeelle ja mitk�� ovat hapettumisen seuraavat vaiheet. T��h��n kysymykseen haetaan vastauksia t��ss�� ty��ss�� k��ytt��en puhtaasti teoreettisia menetelmi�� pinnan k��sittelyss��. Aikaisempien teoreettisten ja kokeellisten tutkimusten v��lill�� on pieni ristiriita liittyen hapen tarttumistodenn��k��isyyteen. Teoreettisten tutkimusten mukaan happi ei puhtaalle pinnalle tullessaan n��e potentiaalivallia, mutta kokeelliset tutkimukset osoittavat sellaisen kuitenkin olevan. Tuohon ristiriitaan pureudutaan k��ytt��en aikaisemmista laskuista poikkeavaa kvanttimekaaniseen molekyylidynamiikkaan perustuvaa l��hestymistapaa. Ty��ss�� havaitaan, ett�� aikaisemmin yleisesti k��ytetty menetelm�� hukkaa huomattavan m����r��n tietoa ja siten tutkijat eiv��t voi ainoastaan tyyty�� tarkastelemaan kyseisell�� menetelm��ll�� saatuja tuloksia. Kuparipinnalle havaittiin, ett�� korkeilla molekyylin kineettisen energian arvolla aikaisemmin suoritetut laskut hajottavista trajektoreista pit��v��t paikkansa, mutta matalilla kineettisen energian arvoilla molekyyli kohtaa eritt��in voimakkaan ``steering'' vaikutuksen ja trajektorit joiden piti olla hajottavia johtavatkin molekulaariseen adsorptioon. Kun hapen konsentraatio pinnalla on suurempi kuin 0.5 ML, pinta rekonstruoituu. My��s rekonstruktion j��lkeist�� pintaa on tutkittu samanlaisilla menetelmill�� kuin puhdasta pintaa. Rekonstruoituneelle pinnalle ei l��ydetty hajottavia trajektoreita ja havaittiin, ett�� hapelle annetun kineettisen energian matalilla arvoilla my��s t��ss�� tapauksessa on eritt��in voimakas ``steering'' vaikutus.