Evaluation of Inductively Coupled Plasma Mass Spectrometry for Determining Ca, Cu, Fe, Mg, Mn, Se and Zn in Bovine Semen Samples using a Simple Sample Dilution Method

A simple and fast method for the determination of Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen by quadrupole inductively coupled plasma spectrometry (q-ICP-MS) is described. Prior to analysis, samples (200 mu L) were diluted 1:50 in a solution containing 0.01% v/v Triton (R) X-100 and 0.5% v/v nitric acid and directly analyzed by ICP-MS. The limits of detection of the method are 0.3, 0.03, 0.2, 0.04, 0.04, 0.03 and 0.03 mu g L-1 for Ca-44, Cu-63, Fe-57, Mg-24, Zn-64, Se-82 and Mn-55, respectively. For purposes of comparison and method validation, four ordinary bovine semen samples were directly analyzed by ICP-MS and by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GF AAS), with no statistical difference between the techniques at the 95% level when applying the t-test. Then, the proposed method was applied in the determinations of Ca, Cu, Fe, Mg, Mn, Se and Zn in collected samples of bovine semen from different breeds, which are used in reproduction programs and artificial insemination.

Caracterização de uma floresta estacional semidecidual em Varginha, MG. E comparação com remanescentes da região.

Foi realizado o levantamento florístico e fitossociológico na porção mais extensa de mata no Parque Florestal Municipal São Francisco de Assis, na cidade de Varginha, sul de Minas Gerais. A área tem cerca de 10 ha e é cortada por um pequeno córrego. Foram lançadas 25 parcelas de 20m x 20m e medidos e cadastrados todos os indivíduos arbóreos com DAP > 5cm. Foram encontrados 1568 indivíduos que, juntos, somaram área basal de 23,65 m2, sendo registrados 102 espécies, 72 gêneros e 42 famílias no levantamento fitossociológico e 111 espécies, 77 gêneros e 43 famílias no levantamento florístico. As famílias com maior número de espécies foram Myrtaceae, Fabaceae e Melastomataceae. As espécies de maior valor de importância foram Casearia arborea, Copaifera langsdorffii, Tachigali rugosa e Myrcia splendens. Os resultados encontrados são os esperados para as Florestas Estacionais Semideciduais da região.

Distribuição vertical dos sistemas de polinização bióticos em áreas de cerrado sentido restrito no Triângulo Mineiro, MG, Brasil

Alguns fatores podem influenciar a distribuição dos recursos florais e sistemas de polinização bióticos nos ecossistemas, como por exemplo, o clima, a altitude, a região geográfica, fragmentação de áreas naturais e as diferenças na composição florística na estratificação vertical. Este estudo teve por objetivo avaliar a distribuição dos sistemas de polinização bióticos na estratificação vertical em fragmentos de cerrado sentido restrito no Triângulo Mineiro. Não houve diferença significativa (χ²0,05,9 =14,17; p = 0,12) na riqueza florística geral entre os fragmentos, nem quando comparada em separado para cada estrato (arbóreo, arbustivo, herbáceo e liana), estando o estrato arbustivo mais bem representado. Da mesma forma, não houve diferenças significativas entre fragmentos quanto aos sistemas de polinização (χ²0,05,21 =13,80; p = 0,8778), sendo a polinização por abelhas mais comum, correspondendo ao menos 85% das espécies de plantas em cada fragmento. Em termos relativos, as plantas polinizadas por abelhas foram dominantes em todos os estratos, chegando a 100% das lianas e herbáceas em alguns fragmentos. Neste estudo, com base na composição florística e distribuição dos sistemas de polinização na estratificação vertical, podemos caracterizar um mosaico vertical no cerrado sentido restrito, que tem implicações na sustentabilidade das comunidades no cerrado, assim como os mosaicos horizontais de fitofisionomias.

Evaluation of inductively coupled plasma mass spectrometry for determining Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen samples using a simple sample dilution method

A simple and fast method for the determination of Ca, Cu, Fe, Mg, Mn, Se and Zn in bovine semen by quadrupole inductively coupled plasma spectrometry (q-ICP-MS) is described. Prior to analysis, samples (200 µL) were diluted 1:50 in a solution containing 0.01% v/v Triton® X-100 and 0.5% v/v nitric acid and directly analyzed by ICP-MS. The limits of detection of the method are 0.3, 0.03, 0.2, 0.04, 0.04, 0.03 and 0.03 µg L-1 for 44Ca, 63Cu, 57Fe, 24Mg, 64Zn, 82Se and 55Mn, respectively. For purposes of comparison and method validation, four ordinary bovine semen samples were directly analyzed by ICP-MS and by flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GF AAS), with no statistical difference between the techniques at the 95% level when applying the t-test. Then, the proposed method was applied in the determinations of Ca, Cu, Fe, Mg, Mn, Se and Zn in collected samples of bovine semen from different breeds, which are used in reproduction programs and artificial insemination.

Composição e estrutura arbórea em floresta estacional semidecidual no Espinhaço Meridional (Serra do Cipó, MG)

Estudos florísticos e fitossociológicos têm sido feitos em áreas de Mata Atlântica, sendo parte desses em remanescentes de Floresta Estacional Semidecidual. Entretanto, no cômputo geral, as florestas na Serra do Espinhaço têm sido pouco estudadas. Este trabalho objetiva descrever e analisar a composição e estrutura de espécies arbóreas de uma área de Floresta Estacional Semidecidual na face leste da Serra do Cipó, porção meridional da Serra do Espinhaço (MG). O método de ponto-quadrante foi utilizado para estudo fitossociológico, sendo o levantamento florístico total incrementado por coletas não-sistematizadas. Foram calculados: área basal total, densidade, frequência e dominância relativas, além do índice de valor de importância. O levantamento florístico total registrou 280 espécies, número que destaca a riqueza da área, cuja maior afinidade florística é com outras áreas florestais localizadas nas bacias dos Rios Doce e Paraíba do Sul. Os parâmetros fitossociológicos destacam a predominância de espécies pioneiras e secundárias iniciais, o que, assim como os valores estruturais, caracteriza um estádio secundário inicial a intermediário de regeneração. Os dados deste trabalho realçam a importância da preservação das florestas estacionais da Mata Atlântica e, particularmente, de áreas florestais na porção leste do Espinhaço.

A theoretical study of the characterization and the absorption spectrum of Mg: Tetracycline complexes in aqueous environment.

The complex formed by the tetracycline (TC) molecule with the Mg ion is able to prevent the replication of the genetic material in the bacterial ribosome, making an excellent antibiotic. In general, the absorption and emission spectra of TC are very sensitive to the host ions and the pH of the solvent that the set is immersed. However, the theoretical absorption spectrum available in the literature is scarce and limited to simple models that do not consider the fluctuations of the liquid. Our aim is to obtain the electronic absorption spectrum of TC and the complex Mg:TC in the ratio 1:1 and 2:1. Moreover, we analyze the changes in intensity and shifts of the bands in the systems listed. We performed the simulation using the classical Monte Carlo technique with the Lennard-Jones plus Coulomb potential applied to each atom of the both TC molecule and the Mg:TC complexes in water. The electronic absorption spectrum was obtained from the time-dependent density functional theory using different solvent models. In general, we obtained a good qualitative description of the spectra when compared with the experimental results. The Mg atom shifts the first band by 4 nm in our models, in excellent agreement to the experimental result of 4 nm. The second absorption band is found here to be useful for the characterization of the position where the ion attaches to the TC.

Mg for hydrogen storage: synthesis, nanostructure and thermodynamics properties

Nowadays alternative energies are an extremely important topic and the possibility of using hydrogen as an energy carrier must be explored. Many problems infer the technological application of this abundant and powerful resource, one of them the possibility of storage. In the framework of suitable materials for hydrogen storage, magnesium has been the center of this study because it is cheap and the amount of stored hydrogen that it achieves (7.6 wt%) is extremely appealing. Nanostructure helps to overcome the slow hydrogen diffusion and the functionalization of surfaces with transition metals or oxides favors the hydrogen molecule dissociation/recombination. The aim of this research is the investigation of the metal-hydride transformation in magnesium nanoparticles synthesized by inert-gas condensation, exploiting the fact that they are a simple model system. The so produced nanostructured powder has been analyzed in response to nanoparticles surface functionalization by transition metal clusters, specifically palladium, nickel and titanium, chosen on the basis of their completely different Mg-related phase diagrams. The role of the intermetallic phases formed upon heating and hydrogenation treatments will be presented to provide a comprehensive picture of hydrogen sorption in this class of nanostructured storage materials.

Ground state properties of neutron-rich Mg isotopes

Studies in regions of the nuclear chart in which the model predictions of properties of nuclei fail can bring a better understanding of the strong interaction in the nuclear medium. To such regions belongs the so called "island of inversion" centered around Ne, Na and Mg isotopes with 20 neutrons in which unexpected ground-state spins, large deformations and dense low-energy spectra appear. This is a strong argument that the magic N = 20 is not a closed shell in this area. In this thesis investigations of isotope shifts of stable 24,25,26Mg, as well as spins and magnetic moments of short-lived 29,31Mg are presented. The successful studies were performed at the ISOLDE facility at CERN using collinear laser and beta-NMR spectroscopy techniques. The isotopes were investigated as single-charged ions in the 280-nm transition from the atomic ground state 2S1/2 to one of the two lowest excited states 2P1/2,3/2 using continuous wave laser beams. The isotope-shift measurements with fluorescence detection for the three stable isotopes show that it is feasible to perform the same studies on radioactive Mg isotopes up to the "island of inversion". This will allow to determine differences in the mean charge square radii and interpret them in terms of deformation. The high detection efficiency for beta particles and optical pumping close to saturation allowed to obtain very good beta-asymmetry signals for 29Mg and 31Mg with half-lives around 1 s and production yields about 10^5 ions/s. For this purpose the ions were implanted into a host crystal lattice. Such detection of the atomic resonances revealed their hyperfine structure, which gives the sign and a first estimate of the value of the magnetic moment. The nuclear magnetic resonance gave also their g-factors with the relative uncertainty smaller than 0.2 %. By combining the two techniques also the nuclear spin of both isotopes could be unambiguously determined. The measured spins and g-factors show that 29Mg with 17 neutrons lies outside the "island of inversion". On the other hand, 31Mg with 19 neutrons has an unexpected ground-state spin which can be explained only by promoting at least two neutrons across the N = 20 shell gap. This places the above nucleus inside the "island". However, modern shell-model approaches cannot predict this level as the ground state but only as one of the low-lying states, even though they reproduce very well the experimental g-factor. This indicates that modifications to the available interactions are required. Future measurements include isotope shift measurements on radioactive Mg isotopes and beta-NMR studies on 33Mg.

In-situ DRIFT/MS study of the conversion of ethanol on mixed Mg/Si oxides

Due to the high price of natural oil and harmful effects of its usage, as the increase in emission of greenhouse gases, the industry focused in searching of sustainable types of the raw materials for production of chemicals. Ethanol, produced by fermentation of sugars, is one of the more interesting renewable materials for chemical manufacturing. There are numerous applications for the conversion of ethanol into commodity chemicals. In particular, the production of 1,3-butadiene whose primary source is ethanol using multifunctional catalysts is attractive. With the 25% of world rubber manufacturers utilizing 1,3-butadiene, there is an exigent need for its sustainable production. In this research, the conversion of ethanol in one-step process to 1,3-butadiene was studied. According to the literature, the mechanisms which were proposed to explain the way ethanol transforms into butadiene require to have both acid and basic sites. But still, there are a lot of debate on this topic. Thus, the aim of this research work is a better understanding of the reaction pathways with all the possible intermediates and products which lead to the formation of butadiene from ethanol. The particular interests represent the catalysts, based on different ratio Mg/Si in comparison to bare magnesia and silica oxides, in order to identify a good combination of acid/basic sites for the adsorption and conversion of ethanol. Usage of spectroscopictechniques are important to extract information that could be helpful for understanding the processes on the molecular level. The diffuse reflectance infrared spectroscopy coupled to mass spectrometry (DRIFT-MS) was used to study the surface composition of the catalysts during the adsorption of ethanol and its transformation during the temperature program. Whereas, mass spectrometry was used to monitor the desorbed products. The set of studied materials include MgO, Mg/Si=0.1, Mg/Si=2, Mg/Si=3, Mg/Si=9 and SiO2 which were also characterized by means of surface area measurements.

Valutazione dell'effetto del mezzo temprante sulle tensioni residue e proprieta meccaniche della lega di alluminio Al-Si7-Mg

L’alluminio, grazie alla sua bassa temperatura di fusione e all’elevata fluidità di molte leghe, è uno dei metalli più versatili in fonderia. Per ottenere il massimo delle proprietà resistenziali, le leghe che lo permettono sono sottoposte a trattamento termico. Questo, però, in componenti geometricamente complessi può far insorgere tensioni residue che inficeranno la resistenza del materiale durante la sua messa in esercizio. Gli obiettivi della presente ricerca sono stati: la valutazione dell’incidenza del mezzo temprante usato durante il trattamento termico sulle tensioni residue che si sviluppano nella lega AlSi7Mg e la definizione di come questo potesse essere modificato per ridurre le tensioni senza peggiorare le proprietà resistenziali del materiale. Per tale ragione sono state eseguite prove di trattamento termico, analisi microstrutturali e test di durezza su campioni estratti direttamente da getti colati in sabbia.

Studio della reattività di etanolo in fase gas su catalizzatori a base di MgO e Mg/Si/O

A causa delle questioni economiche ed ambientali legate alla sostenibilità dei processi petrolchimici, recentemente l'industria chimica ha focalizzato il proprio interesse nello sviluppo di processi per la produzione di chemicals, che utilizzino materiali di partenza rinnovabili. L'etanolo, prodotto per via fermentativa, sembra essere uno dei bio-building block più promettenti e versatili e può essere utilizzato per numerose applicazioni. È noto da tempo che l’etanolo può reagire su catalizzatori costituiti da ossidi misti con caratteristiche acido-base a dare numerosi composti chimici tra cui acetaldeide, 1,3-butadiene, 1-butanolo e 2-butenale. Nonostante il lungo impiego dell’etanolo nell’industria chimica, il meccanismo di formazione di composti C4 a partire da etanolo è ancora però materia di dibattito. Il meccanismo generalmente accettato si basa sulle seguenti reazioni chiave: deidrogenazione di etanolo ad acetaldeide e condensazione aldolica di due molecole di acetaldeide. Tuttavia in letteratura sono riportate anche altre proposte alternative. In questo lavoro è stato studiato il processo di trasformazione di etanolo su catalizzatori a base di MgO e sistemi misti Mg/SiO, attraverso esperimenti di reattività condotti in un micro-impianto da laboratorio, al fine di fare chiarezza sul meccanismo di formazione di composti C4 a partire da etanolo. In particolare è stato condotto uno studio meccanicistico utilizzando MgO come catalizzatore modello, materiale che possiede esclusivamente proprietà basiche, ritenute essenziali per catalizzare la condensazione di molecole C2. Inoltre, è stata investigata l’influenza delle caratteristiche acido-base del catalizzatore sulla selettività del processo di conversione di etanolo, studiandone la reattività su materiali costituiti da ossidi misti Mg/Si/O, con diverso rapporto atomico tra i due cationi.

Il sistema mg-ti nanostrutturato per lo stoccaggio d'idrogeno allo stato solido

Nella presente tesi ci si pone lo scopo di studiare stabilità, ciclabilità e cinetica di campioni composti da magnesio e titanio (Mg-Ti) prodotti con la tecnica della condensazione in gas inerte (IGC) per lo di stoccaggio di idrogeno. Il sistema Mg-Ti sembra essere un buon candidato per poter costruire serbatoi di idrogeno allo stato solido sia per applicazioni fisse che mobili. La ricerca di tecnologie efficaci per immagazzinare idrogeno è fondamentale per poter affermare un ciclo energetico sostenibile, svincolato dai combustibili fossili. Sia il lavoro di crescita dei campioni all'Università di Bologna, sia la caratterizzazione di questi nei laboratori dell' Institut de Chimie et des Materiaux Paris-Est (ICMPE) si collocano all'interno del progetto europeo COST per la ricerca di materiali nanostrutturati destinati ad applicazioni nel campo dello stoccaggio dell'energia in forma di idrogeno allo stato solido.

Experimental investigation of the reactions 25 Mg(alpha,n)28 Si, 26 Mg(alpha,n)29 Si, 18 O(alpha,n)21 Ne and their impact on stellar nucleosynthesis

In der vorliegenden Dissertation werden die Kernreaktionen 25Mg(alpha,n)28Si, 26Mg(alpha,n)29Si und 18O(alpha,n)21Ne im astrophysikalisch interessanten Energiebereich von E alpha = 1000 keV bis E alpha = 2450 keV untersucht.rnrnDie Experimente wurden am Nuclear Structure Laboratory der University of Notre Dame (USA) mit dem vor Ort befindlichen Van-de-Graaff Beschleuniger KN durchgeführt. Hierbei wurden Festkörpertargets mit evaporiertem Magnesium oder anodisiertem Sauerstoff mit alpha-Teilchen beschossen und die freigesetzten Neutronen untersucht. Zum Nachweis der freigesetzten Neutronen wurde mit Hilfe von Computersimulationen ein Neutrondetektor basierend auf rn3He-Zählrohren konstruiert. Weiterhin wurden aufgrund des verstärkten Auftretens von Hintergrundreaktionen verschiedene Methoden zur Datenanalyse angewendet.rnrnAbschliessend wird mit Hilfe von Netzwerkrechnungen der Einfluss der Reaktionen 25Mg(alpha,n)28Si, 26Mg(alpha,n)29Si und 18O(alpha,n)21Ne auf die stellare Nukleosynthese untersucht.rn

Microscopia elettronica di nanoparticelle mg-pd e mg-ti per stoccaggio di idrogeno.

L'utilizzo dell'idrogeno come vettore energetico �è negli ultimi anni uno dei temi in maggior rilievo riguardo la sostenibilit�à energetica, questo per via della sua abbondanza in natura, della sua elevata energia chimica per unità di massa, e della non tossicità dei prodotti della sua combustione. Tuttavia non si conosce ancora una maniera e�fficiente di immagazzinarlo per poterlo utilizzare per applicazioni mobili. In questo lavoro di tesi sono state cresciute, e analizzate mediante microscopia elettronica, nanoparticelle di magnesio decorate con metalli di transizione (Pd e Ti), che si collocano tra i candidati più promettenti per lo stoccaggio di idrogeno a stato solido.

Preparation of cold Mg + ion clouds for sympathetic cooling of highly charged ions at SPECTRAP

Die Elektronen in wasserstoff- und lithium-ähnlichen schweren Ionen sind den extrem starken elektrischen und magnetischen Feldern in der Umgebung des Kerns ausgesetzt. Die Laserspektroskopie der Hyperfeinaufspaltung im Grundzustand des Ions erlaubt daher einen sensitiven Test der Quantenelektrodynamik in starken Feldern insbesondere im magnetischen Sektor. Frühere Messungen an wasserstoffähnlichen Systemen die an einer Elektronenstrahl-Ionenfalle (EBIT) und am Experimentierspeicherring (ESR) der GSI Darmstadt durchgeführt wurden, waren in ihrer Genauigkeit durch zu geringe Statistik, einer starken Dopplerverbreiterung und der großen Unsicherheit in der Ionenenergie limitiert. Das ganze Potential des QED-Tests kann nur dann ausgeschöpft werden, wenn es gelingt sowohl wasserstoff- als auch lithium-ähnliche schwere Ionen mit einer um 2-3 Größenordnung gesteigerten Genauigkeit zu spektroskopieren. Um dies zu erreichen, wird gegenwärtig das neue Penningfallensystem SPECTRAP an der GSI aufgebaut und in Betrieb genommen. Es ist speziell für die Laserspektroskopie an gespeicherten hochgeladenen Ionen optimiert und wird in Zukunft von HITRAP mit nierderenergetischen hochgeladenen Ionen versorgt werden.rnrnSPECTRAP ist eine zylindrische Penningfalle mit axialem Zugang für die Injektion von Ionen und die Einkopplung eines Laserstrahls sowie einem radialen optischen Zugang für die Detektion der Fluoreszenz. Um letzteres zu realisieren ist der supraleitende Magnet als Helmholtz-Spulenpaar ausgelegt. Um die gewünschte Genauigkeit bei der Laserspektroskopie zu erreichen, muss ein effizienter und schneller Kühlprozess für die injizierten hochegeladenen Ionen realisiert werden. Dies kann mittels sympathetischer Kühlung in einer lasergekühlten Wolke leichter Ionen realisiert werden. Im Rahmen dieser Arbeit wurde ein Lasersystem und eine Ionenquelle für die Produktion einer solchen 24Mg+ Ionenwolke aufgebaut und erfolgreich an SPECTRAP in Betrieb genommen. Dazu wurde ein Festkörperlasersystem für die Erzeugung von Licht bei 279.6 nm entworfen und aufgebaut. Es besteht aus einem Faserlaser bei 1118 nm der in zwei aufeinanderfolgenden Frequenzverdopplungsstufen frequenzvervierfacht wird. Die Verdopplerstufen sind als aktiv stabilisierte Resonantoren mit nichtlinearen Kristallen ausgelegt. Das Lasersystem liefert unter optimalen Bedingeungen bis zu 15 mW bei der ultravioletten Wellenlänge und erwies sich während der Teststrahlzeiten an SPECTRAP als ausgesprochen zuverlässig. Desweiteren wurde eine Ionequelle für die gepulste Injektion von Mg+ Ionen in die SPECTRAP Falle entwickelt. Diese basiert auf der Elektronenstoßionisation eines thermischen Mg-Atomstrahls und liefert in der gepulsten Extraktion Ionenbündel mit einer kleinen Impuls- und Energieverteilung. Unter Nutzung des Lasersystems konnten damit an SPECTRAP erstmals Ionenwolken mit bis zu 2600 lasergekühlten Mg Ionen erzeugt werden. Der Nachweis erfolgte sowohl mittels Fluoreszenz als auch mit der FFT-ICR Technik. Aus der Analyse des Fluoreszenz-Linienprofils lässt sich sowohl die Sensitivität auf einzelne gespeicherte Ionen als auch eine erreichte Endtemperatur in der Größenordnung von ≈ 100 mK nach wenigen Sekunden Kühlzeit belegen.