Szilárdmintás spektrokémiai módszerek tanulmányozása optikai kristályok elemzésére = Study on solid sampling spectrochemical methods for the analysis of optical crystals

Szilárdmintás és oldatos grafitkemencés atomabszorpciós spektrometriai (GFAAS) módszereket tanulmányoztunk és dolgoztunk ki lítium-niobát és bizmut-tellurit optikai kristályok adalékelemeinek (Cr, Fe, Mn, Er, Nd, Tm, Zr, Pr és Yb) meghatározására. A szilárdmintás GFAAS módszereket az oldatos GFAAS módszer alapján optimáltuk, amely alkalmasnak bizonyult a szilárdmintás módszer kalibrációjára (hárompont-becsléses standard addíció). A grafitkemence hevítési ciklus (analízis) során nehezen elpárolgó minta-összetevők által keltett memóriahatás megszüntetésére egy leegyszerűsített halogénezéses módszert javasoltunk. A röntgen-abszorpciós él-közeli struktúra (X-ray absorption near-edge structure – XANES) technikával meghatároztuk a grafitkemencében a memóriahatás miatt visszamaradó mintaösszetevők kémiai formáit. A kidolgozott GFAAS módszerek egyszerűen adaptálhatók a grafitkemencés elektrotermikus párologtatós (GF-ETV) csatolt analitikai technikákhoz. A szilárdmintás módszerek validálásához oldatos GFAAS, lángatomabszorpciós spektrometriás (FAAS), induktív csatolású plazma atom emissziós spektrometriás (ICP-AES) és induktív csatolású plazma tömegspektrometriás (ICP-MS) módszereket dolgoztunk ki és alkalmaztunk. | Solid sampling and solution based graphite furnace atomic absorption spectrometry (GFAAS) methods were studied and elaborated to the determination of specific dopant elements (Cr, Fe, Mn, Er, Nd, Tm, Zr, Pr and Yb) in lithium niobate and bismuth tellurite optical crystals. The solid sampling GFAAS methods were optimized on the base of the solution based GFAAS methods, which was also proven to be applicable to the calibration of the solid sampling based method (three-point estimation standard addition). To overcome the memory-effects arising from the slow vaporization of refractory sample components during the heating of the graphite furnace (analytical cycle), a simplified halogenation method was suggested. The chemical forms of the refractory matrix components retained in the graphite furnace due to the memory-effect were determined by X-ray absorption near-edge structure (XANES). The elaborated GFAAS methods can be easily adapted to the graphite furnace electrothemal vaporization (GF-ETV) coupled analytical techniques. For the validation of the solid sampling methods, solution-based GFAAS, flame atomic absorption spectrometry (FAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) methods were elaborated and applied

Factor-of-iid balanced orientation of non-amenable graphs

We show that if a non-amenable, quasi-transitive, unimodular graph $G$ has all degrees even then it has a factor-of-iid balanced orientation, meaning each vertex has equal in- and outdegree. This result involves extending earlier spectral-theoretic results on Bernoulli shifts to the Bernoulli graphings of quasi-transitive, unimodular graphs. As a consequence, we also obtain that when $G$ is regular (of either odd or even degree) and bipartite, it has a factor-of-iid perfect matching. This generalizes a result of Lyons and Nazarov beyond transitive graphs.Comment: 24 pages, 1 figure. This is one of two papers that are replacing the shorter arXiv submission arXiv:2101.12577v1 Factor of iid Schreier decoration of transitive graph

Lézer-ablációs és elektrotermikus mintabeviteli módszerek fejlesztése elemeloszlások atomspektrometriás vizsgálatára = Development of laser ablation and electrothermal sample introduction methods for atomic spectrometry of element distributions

Zárójelentés (2006) Összefoglalás Cím: Lézerablációs és elektrotermikus mintabeviteli módszerek fejlesztése elemeloszlások atomspektrometriás vizsgálatára Az elemzendő minták elektrotermikus párologtatásával (ETV) vagy nagy teljesítményű lézersugárral végzett ablációjával (LA) keltett gőzökből szilárd aeroszol állítható elő hideg argon turbulens hozzákeverésével. A keletkező finom eloszlású aeroszol nagymértékű kicsapódás nélkül szállítható át induktív csatolású plazmamába (ICP), mely utóbbi fényforrásként vagy ionforrásként szolgál az optikai spektroszkópiai (OES) vagy tömegspektroszkópiai (MS) mérőrendszerekhez. A jelen kutatási periódusban a kétféle módszer elvi-elméleti sajátságait az aeroszol képződése szempontjából, egy megjelenés alatt álló könyvfejezetben tárgyaltuk. Kísérleti munkánkban az ETV módszer került előtérbe, melynek eredményeit három megjelent és egy megjelenés alatt álló közleményben ismertettük. Megállapításaink az ETV gázáramoltatásának optimálása, valamint a mintához vagy a gáztérbe adagolt kémiai módosítók kiválasztásában és hatásmechanizmusának felderítésében újszerűek. Ezen kutatásokban hollandiai (Delft) és németországi (Kempten) laboratóriumokkal működtünk együtt. | Development of laser ablation and electrothermal sample introduction methods for atomic spectrometry of element distributions By electrothermal vaporization (ETV) or laser ablation (LA) of samples dry aerosols are produced from the evolved vapor through a turbulent mixing with cold argon gas. The aerosol of high dispersion can be transported without an extensive loss into an inductively plasma (ICP), which can serve either as a light source for optical emission spectroscopic (OES), or as an ion source for mass spectroscopic (MS) measurement systems. In the four years period of research the fundamental characteristics of these two methods with respect of aerosol formation were described in a book chapter which is under publication. In the experimental work, the ETV method came into the forth, the results of which have been discussed in three published papers and in an accepted manuscript. Novel statements could be established to the optimization of the gas streaming conditions in the ETV units, and in exploring the mechanisms of action of chemical modifiers applied either to the samples or to gas phase of the furnace. These research works were done in cooperation with a laboratory in The Netherlands (Delft) and with another laboratory in Germany (Kempten)

Invariant Random Subgroups of Groups Acting on Rooted Trees

We investigate invariant random subgroups in groups acting on rooted trees. Let $\mathrm{Alt}_f(T)$ be the group of finitary even automorphisms of the $d$-ary rooted tree $T$. We prove that a nontrivial ergodic IRS of $\mathrm{Alt}_f(T)$ that acts without fixed points on the boundary of $T$ contains a level stabilizer, in particular it is the random conjugate of a finite index subgroup. Applying the technique to branch groups we prove that an ergodic IRS in a finitary regular branch group contains the derived subgroup of a generalized rigid level stabilizer. We also prove that every weakly branch group has continuum many distinct atomless ergodic IRS's. This extends a result of Benli, Grigorchuk and Nagnibeda who exhibit a group of intermediate growth with this property.Comment: Minor revision, accepted in Transactions of the AMS; 32 pages with Appendix, 4 figure

Mass and ionic composition of atmospheric fine particles over Belgium and their relation with gaseous air pollutants

Original article can be found at: http://www.rsc.org/publishing/journals/EM/Index.asp Copyright Royal Society of Chemistry. DOI: 10.1039/b805157gMass, major ionic components (MICs) of PM2.5, and related gaseous pollutants (SO2, NOx, NH3, HNO2, and HNO3) were monitored over six locations of different anthropogenic influence (industrial, urban, suburban, and rural) in Belgium. SO42-, NO3- NH4+, and Na+ were the primary ions of PM2.5 with averages diurnal concentrations ranging from 0.4-4.5, 0.3-7.6, 0.9-4.9, and 0.4-1.2 g/m3, respectively. MICs formed 39% of PM2.5 on an average, but it could reach up to 80-98 %. The SO2, NO, NO2, HNO2, and HNO3 levels showed high seasonal and site-specific fluctuations. The NH3 levels were similar over all the sites (2-6 g/m3), indicating its relation to the evenly distributed animal husbandry activities. The sulfur and nitrogen oxidation ratios for PM2.5 point towards a low-to-moderate formation of secondary sulfate and nitrate aerosols over five cities/towns, but their fairly intensive formation at the rural Wingene. Cluster analysis revealed the association of three groups of compounds in PM2.5; (i) NH4NO3, KNO3; (ii) Na2SO4; and (iii) MgCl2, CaCl2, MgF2, CaF2, corresponding to anthropogenic, sea-salt, and mixed (sea-salt + anthropogenic) aerosols, respectively. The neutralization and cation-to-anion ratios indicate that MICs of PM2.5 appeared mostly as (NH4)2SO4 and NH4NO3 salts. Sea-salt input was maximal during winter reaching up to 12 % of PM2.5. The overall average Cl-loss for sea-salt particles of PM2.5 at the six sites varied between 69 and 96 % with an average of 87 %. Principal component analysis revealed vehicular emission, coal/wood burning and animal farming as the dominating sources for the ionic components of PM2.5.Peer reviewe

Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air

The daily and seasonal atmospheric concentrations, deposition fluxes and emission sources of a few C3-C9 gaseous alkyl nitrates (ANs) at the Belgian coast (De Haan) on the Southern North Sea were determined. An adapted sampler design for low- and high-volume air-sampling, optimized sample extraction and clean-up, as well as identification and quantification of ANs in air samples by means of gas chromatography mass spectrometry, are reported. The total concentrations of ANs ranged from 0.03 to 85 pptv and consisted primarily of the nitro-butane and nitro-pentane isomers. Air mass backward trajectories were calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine the influence of main air masses on AN levels in the air. The shorter chain ANs have been the most abundant in the Atlantic/Channel/UK air masses, while longer chain ANs prevailed in continental air. The overall mean N fluxes of the ANs were slightly higher for summer than those for winter-spring, although their contributions to the total nitrogen flux were low. High correlations between AN and HNO2 levels were observed during winter/spring. During summer, the shorter chain ANs correlated well with precipitation. Source apportionment by means of principal component analysis indicated that most of the gas phase ANs could be attributed to traffic/combustion, secondary photochemical formation and biomass burning, although marine sources may also have been present and a contributing factor. © 2014 Springer International Publishing Switzerland

Endothelial-Mesenchymal Transition of Brain Endothelial Cells: Possible Role during Metastatic Extravasation

Cancer progression towards metastasis follows a defined sequence of events described as the metastatic cascade. For extravasation and transendothelial migration metastatic cells interact first with endothelial cells. Yet the role of endothelial cells during the process of metastasis formation and extravasation is still unclear, and the interaction between metastatic and endothelial cells during transendothelial migration is poorly understood. Since tumor cells are well known to express TGF-beta, and the compact endothelial layer undergoes a series of changes during metastatic extravasation (cell contact disruption, cytoskeletal reorganization, enhanced contractility), we hypothesized that an EndMT may be necessary for metastatic extravasation. We demonstrate that primary cultured rat brain endothelial cells (BEC) undergo EndMT upon TGF-beta 1 treatment, characterized by the loss of tight and adherens junction proteins, expression of fibronectin, beta 1-integrin, calponin and a-smooth muscle actin (SMA). B16/F10 cell line conditioned and activated medium (ACM) had similar effects: claudin-5 down-regulation, fibronectin and SMA expression. Inhibition of TGF-beta signaling during B16/F10 ACM stimulation using SB-431542 maintained claudin-5 levels and mitigated fibronectin and SMA expression. B16/F10 ACM stimulation of BECs led to phosphorylation of Smad2 and Smad3. SB-431542 prevented SMA up-regulation upon stimulation of BECs with A2058, MCF-7 and MDA-MB231 ACM as well. Moreover, B16/F10 ACM caused a reduction in trans-endothelial electrical resistance, enhanced the number of melanoma cells adhering to and transmigrating through the endothelial layer, in a TGF-beta-dependent manner. These effects were not confined to BECs: HUVECs showed TGF-beta-dependent SMA expression when stimulated with breast cancer cell line ACM. Our results indicate that an EndMT may be necessary for metastatic transendothelial migration, and this transition may be one of the potential mechanisms occurring during the complex phenomenon known as metastatic extravasation