Measurement of Atmospheric NOy Species Using Active and Lunar DOAS in an Urban and Forested Region

The study of NOy serves as an important undertaking in the understanding of both night and daytime atmospheric processes. Two separate datasets were collected over the course of this research using Differential Optical Absorption Spectroscopy. In the first study, NO3 vertical column densities (VCDs) determined using lunar DOAS were analysed in conjunction with surface mixing ratios found using active DOAS on two separate nights during the summer of 2015 to quantify the NO3 vertical profile present at York University. The second study focused on the determination of HONO mixing ratios based on full-day active DOAS measurements performed in a forested region at the AMS13 site near Fort McMurray, Alberta during a joint field study with Environment Canada. The average diurnal profile of HONO found in this study (and various other species) was used for calculating the daytime production of OH radical through HONO photolysis compared to other OH production mechanisms

Amyloid burden and white matter hyperintensities mediate age-related cognitive differences

This study examined the additive versus synergistic contribution of beta-amyloid (Aβ) and white matter hyperintensities (WMHs) across 7 cognitive domains in 104 cognitively normal older adults. It also measured the extent to which age-related differences in cognition are driven by measurable brain pathology. All participants underwent neuropsychological assessment along with magnetic resonance imaging and Pittsburg compound B-positron emission tomography imaging for Aβ quantification. WMH severity was quantified using the age-related white matter changes scale. Stepwise regressions, moderation, and mediation modeling were performed. Our findings show that Aβ deposition single-handedly predicts poorer episodic memory performance and that Aβ and WMHs contribute additively to poorer performance in working memory and language while carrying synergistic associations with executive functions and attention. Through mediation modeling, we demonstrated that the influence of age over episodic memory, working memory, executive functions, and language is fully mediated by brain pathology. This study permits to conclude that, in healthy older adults, (1) Aβ burden and WMHs have synergistic associations with some cognitive domains and (2) age-related differences in most cognitive domains are driven by brain pathology associated with dementia

Subcortical amyloid relates to cortical morphology in cognitively normal individuals

Purpose Amyloid (Aβ) brain deposition can occur in cognitively normal individuals and is associated with cortical volume abnormalities. Aβ-related volume changes are inconsistent across studies. Since volume is composed of surface area and thickness, the relative contribution of Aβ deposition on each of these metrics remains to be understood in cognitively normal individuals. Methods A group of 104 cognitively normal individuals underwent neuropsychological assessment, PiB-PET scan, and MRI acquisition. Surface-based cortical analyses were performed to investigate the effects of cortical and subcortical Aβ burden on cortical volume, thickness, and surface area. Mediation analyses were used to study the effect of thickness and surface area on Aβ-associated volume changes. We also investigated the relationships between structural metrics in clusters with abnormal morphology and regions underlying resting-state functional networks and cognitive performance. Results Cortical Aβ was not associated with cortical morphology. Subcortical Aβ burden was associated with changes in cortical volume, thickness, and surface area. Aβ-associated volume changes were driven by cortical surface area with or without thickness but never by thickness alone. Aβ-associated changes overlapped greatly with regions from the default mode network and were associated with lower performance in visuospatial abilities, episodic memory, and working memory. Conclusions In cognitively normal individuals, subcortical Aβ is associated with cortical volume, and this effect was driven by surface area with or without thickness. Aβ-associated cortical changes were found in the default mode network and affected cognitive performance. Our findings demonstrate the importance of studying subcortical Aβ and cortical surface area in normal agein

Education as a moderator of the relationship between episodic memory and amyloid load in normal aging

The current study explored whether education, a proxy of cognitive reserve, modifies the association between episodic memory (EM) performance and βeta-amyloid load (Aβ), a biomarker of Alzheimer’s disease, in a cohort of cognitively normal older adults. One hundred and four participants (mean age 73.3 years) evenly spread out in three bands of education were recruited. Participants underwent neuropsychological assessment, structural MRI as well as PET imaging to quantify Aβ load. Moderation analyses and the Johnson–Neyman technique were carried out to examine the interaction of education with Aβ load to predict EM performance. Linear regressions were then performed within each group of education to better illustrate the interaction effect (all analyses were controlled for age and sex). The interaction between education and Aβ load was significant (p < .05) for years of education, reaching a cutoff point of 13.5 years, above which the relationship between Aβ load and EM was no longer significant. Similarly, significant associations were found between Aβ and EM among participants with secondary (p < .01) and preuniversity education (p < .01), but not with a university degree (p = .253). EM performance is associated with Aβ load in cognitively normal older individuals, and this relationship is moderated by educational attainment

Structural brain differences between monolingual and multilingual patients with mild cognitive impairment and Alzheimer disease: Evidence for cognitive reserve

Two independent lines of research provide evidence that speaking more than one language may 1) contribute to increased grey matter in healthy younger and older adults and 2) delay cognitive symptoms in mild cognitive impairment (MCI) or Alzheimer disease (AD). We examined cortical thickness and tissue density in monolingual and multilingual MCI and AD patients matched (within Diagnosis Groups) on demographic and cognitive variables. In medial temporal disease-related (DR) areas, we found higher tissue density in multilingual MCIs versus monolingual MCIs, but similar or lower tissue density in multilingual AD versus monolingual AD, a pattern consistent with cognitive reserve in AD. In areas related to language and cognitive control (LCC), both multilingual MCI and AD patients had thicker cortex than the monolinguals. Results were largely replicated in our native-born Canadian MCI participants, ruling out immigration as a potential confound. Finally, multilingual patients showed a correlation between cortical thickness in LCC regions and performance on episodic memory tasks. Given that multilinguals and monolinguals were matched on memory functioning, this suggests that increased gray matter in these regions may provide support to memory functioning. Our results suggest that being multilingual may contribute to increased gray matter in LCC areas and may also delay the cognitive effects of disease-related atrophy

Synthesis and crystalstructure refinement of oxoborates and chloride oxoborates of trivalent rare earth metals

Untersuchungen an Phasendiagrammen in den Systemen M2O3 – B2O3 (M = Sc, Y, La; Ce – Lu) zeigen die Existenz von drei verschiedenen Formeltypen, ortho-Oxoborate MBO3, meta-Oxoborate M(BO2)3 und Oxid-Oxoborate M3BO6 (&#8801; M3O3[BO3]), die bisher jedoch noch nicht anhand von Einkristalldaten charakterisiert werden konnten. Der Bereich der ortho-Oxoborate MBO3 mit sieben verschiedenen Strukturtypen in Abhängigkeit vom Ionenradius des Selten-Erd-Kations (M3+) und den Darstellungsbedingungen ist gut erforscht. Bei den meta-Oxoboraten M(BO2)3 existieren bisher Einkristallstrukturdaten für die Lanthanide M = La – Gd, bei den Elementen Tb – Lu war die Struktur noch ungeklärt. In dieser Arbeit ist es gelungen, die Kristallstruktur von M(BO2)3 (M = Tb, Dy) anhand von Einkristalldaten zu bestimmen. Dieser orthorhombische Strukturtyp wird aus stark gewellten Schichten aufgebaut. Die B3+-Kationen werden, im Gegensatz zu jenen des bisher bekannten monoklinen Strukturtyps, allesamt tetraedrisch von Sauerstoff umgeben. Auch die Synthese eines ultra-Oxoborates der Zusammensetzung La4B14O27 (orthorhombisch) ist gelungen. Diese Verbindung basiert auf einem Raumgitter, bestehend aus trigonal und tetraedrisch von Sauerstoff umgebenen Borkationen. Im System M2O3 – MCl3 – B2O3 waren bisher zwei Formeltypen bekannt: MCl(BO2)2 (M = La, Pr; triklin), formal ein meta-Oxoborat, in dem eine Oxoborat-Einheit durch ein Cl–-Anion ersetzt wird, und Er2Cl2[B2O5] (orthorhombisch), mit planaren Oxodiborat-Einheiten. Es lag nahe, die Reihe für die Zusammensetzung MCl(BO2)2 mit Ce3+ zu komplettieren. Dabei konnte ein weiterer Formel- und Strukturtyp, M3Cl3[BO3] (M = La, Ce; hexagonal), dargestellt werden. Welche der beiden Verbindungen nun kristallisiert, ist vom stöchiometrischen Verhältnis der eingesetzten Edukte und der Temperatur abhängig. Verbindungen der Zusammensetzung MCl(BO2)2 und M3Cl3[BO3] sind aufgrund der hohen Koordinationszahlen (CN = 10) am M3+-Kation nur für die leichteren, aber größeren Selten-Erd-Kationen (M = La – Nd) zu erwarten. Deshalb ist es interessant, welche Strukturen bei den kleineren, schwereren Selten-Erd-Kationen realisiert werden können. Der Formeltyp M2Cl2[B2O5] war bisher nur mit M = Er darstellbar, nun konnte er auch mit M = Sc realisiert werden. Die Koordinationszahlen am M3+-Kation von sechs und sieben lassen vermuten, daß diese Struktur auch mit den Elementen M = Y; Sm – Lu zugänglich ist. In den bisher genannten Verbindungen kann man, ausgehend vom meta-Oxoborat, formal Borateinheiten durch Cl–-Anionen ersetzen. Dies bedeutet, daß die MCl(BO2)2-Struktur Ketten der Zusammensetzung {[BO2]–} aus eckenverknüpften, trigonal planaren Oxoborat-Einheiten als charakteristische Baueinheit aufweist, da hier nur eine Oxoborat-Einheit ersetzt wurde. In M2Cl2[B2O5] wurden zwei Oxoborat-Einheit durch Cl–-Anionen substituiert, deshalb liegen hier diskrete Oxodiborat-Einheiten [B2O5]4– vor und der formale Austausch einer weiteren Oxoborat-Einheit in M3Cl3[BO3] führt zu isolierten, trigonal planaren Oxoborat-Einheiten [BO3]3– als strukturellem Charakteristikum. Analog zu den noch schlecht charakterisierten Oxid-Oxoboraten wurden erstmals Oxidchlorid-Oxoborate der dreiwertigen Selten-Erd-Elemente synthetisiert. Die Strukturen des Formeltyps M4O4Cl[BO3] (M = Dy – Tm) sind monoklin und weisen eine stark gewellte Schichtstruktur, bestehend aus sauerstoffzentrierten, ecken- und kantenverknüpften Tetraedern [OM4]10+ einerseits sowie diskreten Oxoborat-Einheiten [BO3]3– und Chlorid-Anionen Cl– andererseits auf. Mit Koordinationszahlen von sieben und acht am M3+-Kation ist diese Verbindungsklasse ebenfalls bei den schwereren, kleineren Selten-Erd-Elementen (M = Sc, Y; Eu – Tb, Lu) zu erwarten. Von Interesse wäre es, die dargestellten Verbindungen auf Eigenschaften als „host materials“ für Leuchtstoffe zu untersuchen. Es ist zu erwarten, daß sie einfach und auch mehrfach dotiert interessante Lumineszenzeigenschaften aufweisen, da Boratpräparate hierfür bekannt sind.Investigations into phase diagrams of the systems M2O3 – B2O3 ( M = Sc, Y, La; Ce – Lu) show that three different formula types, ortho-oxoborates MBO3, meta-oxoborates and oxide-oxoborates (&#8801; M3O3[BO3]), exist. However, it has not as yet been possible to characterize the latter by single crystal data. The family of ortho-oxoborates MBO3 is well-studied, with seven different structural types found, independent of the ionic radii of the rare-earth cations (M3+) and reaction conditions. Single crystal data exists for the meta-oxoborates M(BO2)3; for the elements Tb – Lu the structure has not yet been determined. In the current work, it was possible to determine the crystal structure of M(BO2)3 (M = Tb, Dy) from single crystal data. This orthorhombic structural type is made up of strongly undulating sheets. The B3+ cations, in contrast to those of the other known structural types, are in a tetrahedral environment formed by oxygen atoms. The synthesis of an ultra-oxoborate of the form La4B14O27 (orthorhombic) could also be achieved. This compound derives from a three-dimensional network formed from boron cations surrounded trigonally and tetrahedrally by oxygen. In the system M2O3 – MCl3 – B2O3, two formula types are known. MCl(BO2)2 (M = La, Pr; triclinic) are formally meta-oxoborates, where one oxoborate unit is substituted by a Cl– anion, whereas Er2Cl2[B2O5] (orthorhombic) has planar oxodiborate units. This suggested completing the series MCl(BO2)2 with Ce3+. Through this, a further formula and structural type, M3Cl3[BO3] (M = La, Ce; hexagonal) could be obtained. Which of these two compounds crystallizes is dependent on the stoichiometric ratio of the starting materials used and the temperature. Compounds of the form MCl(BO2)2 and M3Cl3[BO3] are only expected for the lighter, larger rare-earth cations (M = La – Nd) due to the high coordination number at the M3+ cation (CN = 10). For this reason, it is of interest to investigate which structures form for the smaller, heavier rare-earth cations. Until now, the formula type M2Cl2[B2O5] could only be obtained for M = Er; it has now been achieved here for M = Sc. Coordination numbers six and seven for the M3+ cations suggest that this structure is also obtainable for the elements M = Y, Sm – Lu. In the compounds mentioned above, borate units from meta-oxoborate can be formally substituted by Cl– anions. As a consequence, the MCl(BO2)2 structure exhibits chains of the form {[BO2]–} of corner-sharing, trigonal planar oxoborate units as the characteristic building block, as here only one oxoborate unit is substituted. In M2Cl2[B2O5], two oxoborate units are substituted by Cl– anions, thus discrete oxodiborate units [B2O5]2– occur here. The formal exchange of a further oxoborate unit in M3Cl3[BO3] leads to isolated, trigonal planar oxoborate units [BO3]3– as the characteristic structural form. Oxide-chloride-oxoborates of the trivalent rare-earth elements could be synthesized for the first time, analogously to the still unsatisfactorily characterized oxide-oxoborates. The structures of the formula type M4O4Cl[BO3] (M = Dy – Tm) are monoclinic and exhibit a strongly undulating sheet structure which is formed of oxygen-centred corner- and edge-sharing tetrahedral [OM4]10+ on one hand and discrete oxoborate units [BO3]3– and chloride anions Cl– on the other. This class of compound, with coordination numbers of seven and eight for the M3+ cations, is also anticipated for the heavier, smaller rare-earth elements (M = Sc, Y, Eu – Tb, Lu). It would be of interest to investigate whether the properties of the compounds synthesized make them suitable as host materials for luminescent substances. Borate preparations are known to exhibit interesting luminescence properties, and it is expected that the compounds would show these, whether singly or multiply doped

Vernetzt — Verlinkt — Verloren?: Hinweise zum Lehren und Lernen mit Hypertexten

Während die Anwendung von Hypertexten im Alltag von Schüler/innen weitgehend selbstverständlich ist, wird dieses Medium im Unterricht bislang wenig verwendet. Vorliegende Arbeit beschreibt die Bedingungen für einen medienadäquaten und lernerfolgsorientierten Einsatz von Hypertexten im Unterricht. Aufbauend auf einer strukturellen Analyse des Mediums und der Darstellung von Lernabläufen werden geeignete Lernziele, Inhalte und Situationen herausgearbeitet, in denen die Lernenden die Möglichkeiten von Hypertexten optimal nutzen, ohne von den vielfältigen Entscheidungsspielräumen überfordert zu sein

Combining positron emission tomography (PET) data with neuroanatomical constraints : comparing models of single-word processing

The focus of this paper is to apply some of the new analytic techniques to positron emission tomography (PET) data in order to test the neuroanatomical plausibility of two very specific models of language processing: the model of Geschwind (1965), and that of Petersen et al. (1988; 1989). Model plausibility was assessed by fitting both models to a word repetition and a synonym generation rCBF PET dataset using methods based on the examination of interregional correlations, and structural equation modeling.Physiologically-based regions of interest were defined a priori through a review of PET activation literature. The current study demonstrated (1) the feasibility of using a priori defined physiological regions of interest in model evaluation, (2) the advantages of using structural equation modeling over interregional correlations, and (3) that neither model proved to be a particularly good fit to the data