A panchromatic view of the evolution of supermassive black holes

This PhD Thesis is devoted to the accurate analysis of the physical properties of Active Galactic Nuclei (AGN) and the AGN/host-galaxy interplay. Due to the broad-band AGN emission (from radio to hard X-rays), a multi-wavelength approach is mandatory. Our research is carried out over the COSMOS field, within the context of the XMM-Newton wide-field survey. To date, the COSMOS field is a unique area for comprehensive multi-wavelength studies, allowing us to define a large and homogeneous sample of QSOs with a well-sampled spectral coverage and to keep selection effects under control. Moreover, the broad-band information contained in the COSMOS database is well-suited for a detailed analysis of AGN SEDs, bolometric luminosities and bolometric corrections. In order to investigate the nature of both obscured (Type-2) and unobscured (Type-1) AGN, the observational approach is complemented with a theoretical modelling of the AGN/galaxy co-evolution. The X-ray to optical properties of an X-ray selected Type-1 AGN sample are discussed in the first part. The relationship between X-ray and optical/UV luminosities, parametrized by the spectral index αox, provides a first indication about the nature of the central engine powering the AGN. Since a Type-1 AGN outshines the surrounding environment, it is extremely difficult to constrain the properties of its host-galaxy. Conversely, in Type-2 AGN the host-galaxy light is the dominant component of the optical/near-IR SEDs, severely affecting the recovery of the intrinsic AGN emission. Hence a multi-component SED-fitting code is developed to disentangle the emission of the stellar populationof the galaxy from that associated with mass accretion. Bolometric corrections, luminosities, stellar masses and star-formation rates, correlated with the morphology of Type-2 AGN hosts, are presented in the second part, while the final part concerns a physically-motivated model for the evolution of spheroidal galaxies with a central SMBH. The model is able to reproduce two important stages of galaxy evolution, namely the obscured cold-phase and the subsequent quiescent hot-phase.

Preparation of new crystal forms via photochemical, mechanochemical and sol-gel methods

This work of thesis involves various aspects of crystal engineering. Chapter 1 focuses on crystals containing crown ether complexes. Aspects such as the possibility of preparing these materials by non-solution methods, i.e. by direct reaction of the solid components, thermal behavior and also isomorphism and interconversion between hydrates are taken into account. In chapter 2 a study is presented aimed to understanding the relationship between hydrogen bonding capability and shape of the building blocks chosen to construct crystals. The focus is on the control exerted by shape on the organization of sandwich cations such as cobalticinium, decamethylcobalticinium and bisbenzenchromium(I) and on the aggregation of monoanions all containing carboxylic and carboxylate groups, into 0-D, 1-D, 2-D and 3-D networks. Reactions conducted in multi-component molecular assemblies or co-crystals have been recognized as a way to control reactivity in the solid state. The [2+2] photodimerization of olefins is a successful demonstration of how templated solid state synthesis can efficiently synthesize unique materials with remarkable stereoselectivity and under environment-friendly conditions. A demonstration of this synthetic strategy is given in chapter 3. The combination of various types of intermolecular linkages, leading to formation of high order aggregation and crystalline materials or to a random aggregation resulting in an amorphous precipitate, may not go to completeness. In such rare cases an aggregation process intermediate between crystalline and amorphous materials is observed, resulting in the formation of a gel, i.e. a viscoelastic solid-like or liquid-like material. In chapter 4 design of new Low Molecular Weight Gelators is presented. Aspects such as the relationships between molecular structure, crystal packing and gelation properties and the application of this kind of gels as a medium for crystal growth of organic molecules, such as APIs, are also discussed.

Structural transformations related to organic solid-state reactions: correlation studies of NMR and X-ray analysis

Eine zielgerichtete Steuerung und Durchführung von organischen Festkörperreaktionen wird unter anderem durch genaue Kenntnis von Packungseffekten ermöglicht. Im Rahmen dieser Arbeit konnte durch den kombinierten Einsatz von Einkristallröntgenanalyse und hochauf-lösender Festkörper-NMR an ausgewählten Beispielen ein tieferes Verständnis und Einblicke in die Reaktionsmechanismen von organischen Festkörperreaktionen auf molekularer Ebene gewonnen werden. So konnten bei der topotaktischen [2+2] Photodimerisierung von Zimt-säure Intermediate isoliert und strukturell charakterisiert werden. Insbesondere anhand statischer Deuteronen- und 13C-CPMAS NMR Spektren konnten eindeutig dynamische Wasserstoffbrücken nachgewiesen werden, die transient die Zentrosymmetrie des Reaktions-produkts aufheben. Ein weiterer Nachweis gelang daraufhin mittels Hochtemperatur-Röntgen-untersuchung, sodass der scheinbare Widerspruch von NMR- und Röntgenuntersuchungen gelöst werden konnte. Eine Veresterung der Zimtsäure entfernt diese Wasserstoffbrücken und erhält somit die Zentrosymmetrie des Photodimers. Weiterhin werden Ansätze zur Strukturkontrolle in Festkörpern basierend auf der molekularen Erkennung des Hydroxyl-Pyridin (OH-N) Heterosynthon in Co-Kristallen beschrieben, wobei vor allem die Stabilität des Synthons in Gegenwart funktioneller Gruppen mit Möglichkeit zu kompetetiver Wasserstoffbrückenbildung festgestellt wurde. Durch Erweiterung dieses Ansatzes wurde die molekulare Spezifität des Hydroxyl-Pyridin (OH-N) Heterosynthons bei gleichzeitiger Co-Kristallisation mit mehreren Komponenten erfolgreich aufgezeigt. Am Beispiel der Co-Kristallisation von trans--1,2-bis(4-pyridyl)ethylen (bpe) mit Resorcinol (res) in Gegenwart von trans-1,2-bis(4-pyridyl)ethan (bpet) konnten Zwischenprodukte der Fest-körperreaktionen und neuartige Polymorphe isoliert werden, wobei eine lückenlose Aufklärung des Reaktionswegs mittels Röntgenanalyse gelang. Dabei zeigte sich, dass das Templat Resorcinol aus den Zielverbindungen entfernbar ist. Ferner gelang die Durchführung einer seltenen, nicht-idealen Einkristall-Einkristall-Umlagerung von trans--1,2-bis(4-pyridyl)ethylen (bpe) mit Resorcinol (res). In allen Fällen konnten die Fragen zur Struktur und Dynamik der untersuchten Verbindungen nur durch gemeinsame Nutzung von Röntgenanalyse und NMR-Spektroskopie bei vergleichbaren Temperaturen eindeutig und umfassend geklärt werden.

New regularization method for EXAFS analysis: Application to uranium and plutonium sorption onto kaolinite

Die Röntgenabsorptionsspektroskopie (Extended X-ray absorption fine structure (EXAFS) spectroscopy) ist eine wichtige Methode zur Speziation von Schwermetallen in einem weiten Bereich von umweltrelevanten Systemen. Um Strukturparameter wie Koordinationszahl, Atomabstand und Debye-Waller Faktoren für die nächsten Nachbarn eines absorbierenden Atoms zu bestimmen, ist es für experimentelle EXAFS-Spektren üblich, unter Verwendung von Modellstrukturen einen „Least-Squares-Fit“ durchzuführen. Oft können verschiedene Modellstrukturen mit völlig unterschiedlicher chemischer Bedeutung die experimentellen EXAFS-Daten gleich gut beschreiben. Als gute Alternative zum konventionellen Kurven-Fit bietet sich das modifizierte Tikhonov-Regularisationsverfahren an. Ergänzend zur Tikhonov-Standardvariationsmethode enthält der in dieser Arbeit vorgestellte Algorithmus zwei weitere Schritte, nämlich die Anwendung des „Method of Separating Functionals“ und ein Iterationsverfahren mit Filtration im realen Raum. Um das modifizierte Tikhonov-Regularisationsverfahren zu testen und zu bestätigen wurden sowohl simulierte als auch experimentell gemessene EXAFS-Spektren einer kristallinen U(VI)-Verbindung mit bekannter Struktur, nämlich Soddyit (UO2)2SiO4 x 2H2O, untersucht. Die Leistungsfähigkeit dieser neuen Methode zur Auswertung von EXAFS-Spektren wird durch ihre Anwendung auf die Analyse von Proben mit unbekannter Struktur gezeigt, wie sie bei der Sorption von U(VI) bzw. von Pu(III)/Pu(IV) an Kaolinit auftreten. Ziel der Dissertation war es, die immer noch nicht voll ausgeschöpften Möglichkeiten des modifizierten Tikhonov-Regularisationsverfahrens für die Auswertung von EXAFS-Spektren aufzuzeigen. Die Ergebnisse lassen sich in zwei Kategorien einteilen. Die erste beinhaltet die Entwicklung des Tikhonov-Regularisationsverfahrens für die Analyse von EXAFS-Spektren von Mehrkomponentensystemen, insbesondere die Wahl bestimmter Regularisationsparameter und den Einfluss von Mehrfachstreuung, experimentell bedingtem Rauschen, etc. auf die Strukturparameter. Der zweite Teil beinhaltet die Speziation von sorbiertem U(VI) und Pu(III)/Pu(IV) an Kaolinit, basierend auf experimentellen EXAFS-Spektren, die mit Hilfe des modifizierten Tikhonov-Regularisationsverfahren ausgewertet und mit Hilfe konventioneller EXAFS-Analyse durch „Least-Squares-Fit“ bestätigt wurden.

Synthesis and characterization of oligo(thiophene carboxamide)s

Die vorliegende Arbeit besteht aus zwei Teilen: Im ersten Teil der Arbeit werden supramolekulare Strukturen betrachtet, die durch unterschiedliche Fällungsbedingungen von Polyethylenoxid-block-oligo-p-benzamid-copolymeren erhalten wurden. Durch tropfenweise Zugabe des gelösten Polymers zu Chloroform, ein für Polyethylenoxid selektives Lösemittel, konnten verschiedenste Aggregate hergestellt werden. Von großen Hohlkugel mit einem Durchmesser von mehreren Mikrometern, bis zu kleinen Stäbchen mit den Abmessungen von zehn Nanometern in der Breite und einigen hundert Nanometern Länge, konnten beobachtet werden.rnDer Hauptteil der Arbeit handelt von der Synthese und Charakterisierung eines neuen, konjugierten Oligomers: Oligothiophencarbonsäureamid. Das hierfür nötige Monomer, eine 2-Aminothiophen-5-carbonsäure konnte mittels Gewald-Synthese, eine multikomponenten Ringschlussreaktion dargestellt werden. Diese Methode erlaubt die Herstellung von vierfach substituierten Thiophenen, wobei 3- und 4-Position meist Alkylketten und Ester sind. Das so hergestellte Material konnte in der stufenweise Synthese von Oligothiophencarbonsäureamiden genutzt werden. Die neuen Oligomere zeigten interessante Absorptions- und Fluoreszenzeigenschaften. In Dichlormethan wurde eine bathochrome Verschiebung der Absorptionsbande in Abhängigkeit der Oligomerlänge beobachtet. Das Pentamer erreichte eine Absorptionsenergie, die der Bande des Polythiophencarbonsäureamids entspricht, was bedeutetet, dass die effektive Konjugationslänge erreicht wurde. Im Gegensatz zu den Messungen in Dichlormethan, zeigten die Oligomere Aggregationstendenzen ab dem Trimer in N,N-Dimethylformamid. Die auftretende Charge-Transfer Bande verschwand mit steigenden Konzentrationen. Eine mögliche hypsochrome Verschiebung dieser Bande, deutet auf eine Bildung von H Aggregaten hin. Fluoreszenz und zeitaufgelöste Fluoreszenzmessungen ergaben die für konjugierte Systeme zu erwartenden Effekte. Die Konjugation entlang des Amids konnte ebenfalls mittels quantenmechanischer Berechnung nachgewiesen werden.

Synthese organisch-anorganischer Hybridmaterialien in Mehrkomponenten-Lösungsmittelsystemen

Die Funktionalisierung anorganischer Nanopartikel stellt einen Schlüsselschritt in der Herstellung von Nanokompositen dar. Nanokomposite erzielen ein wachsendes Interesse im Bereich der Polymer- und der Materialwissenschaften, da die Kombination mehrerer Materialien mit unterschiedlichen Eigenschaften, wie etwa die Kombination anorganischer Nanopartikel mit Polymeren, große Synergieeffekte erhoffen lässt.rnrnDer Einbau anorganischer Nanopartikel in polymere Matrixmaterialien zur Verbesserung oder Einführung mechanischer, optischer oder magnetischer Eigenschaften von Polymeren bedarf allerdings der Modifizierung der Oberfläche des anorganischen Materials, um die für die positiven Synergieeffekte essentielle Kompatibilität zwischen Füllstoff und Matrix zu erreichen.rnrnEine Vielzahl anorganischer Partikel ist bereits als wässrige Dispersion erhältlich (SiO2, Al2O3, CeO2, ZrO2, ...). Mehrkomponenten- Lösungsmittelsysteme ermöglichen den Transfer dieser Partikel in eine unpolare Umgebung und gleichzeitig deren Funktionalisierung mit amphiphilen Copolymeren. Aufgrund der reversiblen Schaltbarkeit dieser Lösungsmittelsysteme zwischen einem einphasigen und zweiphasigen Zustand werden die zu Beginn in zwei nichtmischbaren Phasen vorliegenden Reaktionspartner durch Übergang in einen einphasigen Zustand unter homogenen Bedingungen in Kontakt gebracht und durch eine erneute Phasentrennung isoliert.rnEin weiterer Vorteil dieser Lösungsmittelsysteme ist deren Tolerierung funktioneller Gruppen in den verwendeten amphiphilen Copolymeren, welche nicht in Wechselwirkung mit der Partikeloberfläche stehen. Beispielsweise können Amine in den amphiphilen Copolymeren für die Wechselwirkung der funktionalisierten Partikel mit einer Polyurethanmatrix dienen, Alkine können mittels einer 1,3-dipolaren Cycloaddition umgesetzt werden oder aber perfluorierten Seitenketten in den Seitenketten der amphiphilen Copolymere die Kompatibilisierung der funktionalisierten Partikel mit einem perfluorierten Polymer gewährleisten.

Nanocrystalline Silicon Based Films for Renewable Energy Applications

The present thesis is focused on the study of innovative Si-based materials for third generation photovoltaics. In particular, silicon oxi-nitride (SiOxNy) thin films and multilayer of Silicon Rich Carbide (SRC)/Si have been characterized in view of their application in photovoltaics. SiOxNy is a promising material for applications in thin-film solar cells as well as for wafer based silicon solar cells, like silicon heterojunction solar cells. However, many issues relevant to the material properties have not been studied yet, such as the role of the deposition condition and precursor gas concentrations on the optical and electronic properties of the films, the composition and structure of the nanocrystals. The results presented in the thesis aim to clarify the effects of annealing and oxygen incorporation within nc-SiOxNy films on its properties in view of the photovoltaic applications. Silicon nano-crystals (Si NCs) embedded in a dielectric matrix were proposed as absorbers in all-Si multi-junction solar cells due to the quantum confinement capability of Si NCs, that allows a better match to the solar spectrum thanks to the size induced tunability of the band gap. Despite the efficient solar radiation absorption capability of this structure, its charge collection and transport properties has still to be fully demonstrated. The results presented in the thesis aim to the understanding of the transport mechanisms at macroscopic and microscopic scale. Experimental results on SiOxNy thin films and SRC/Si multilayers have been obtained at macroscopical and microscopical level using different characterizations techniques, such as Atomic Force Microscopy, Reflection and Transmission measurements, High Resolution Transmission Electron Microscopy, Energy-Dispersive X-ray spectroscopy and Fourier Transform Infrared Spectroscopy. The deep knowledge and improved understanding of the basic physical properties of these quite complex, multi-phase and multi-component systems, made by nanocrystals and amorphous phases, will contribute to improve the efficiency of Si based solar cells.

Charge-transport simulations in organic semiconductors

In this thesis we have extended the methods for microscopic charge-transport simulations for organic semiconductors. In these materials the weak intermolecular interactions lead to spatially localized charge carriers, and the charge transport occurs as an activated hopping process between diabatic states. In addition to weak electronic couplings between these states, different electrostatic environments in the organic material lead to a broadening of the density of states for the charge energies which limits carrier mobilities.rnThe contributions to the method development includern(i) the derivation of a bimolecular charge-transfer rate,rn(ii) the efficient evaluation of intermolecular (outer-sphere) reorganization energies,rn(iii) the investigation of effects of conformational disorder on intramolecular reorganization energies or internal site energiesrnand (iv) the inclusion of self-consistent polarization interactions for calculation of charge energies.These methods were applied to study charge transport in amorphous phases of small molecules used in the emission layer of organic light emitting diodes (OLED).rnWhen bulky substituents are attached to an aromatic core in order to adjust energy levels or prevent crystallization, a small amount of delocalization of the frontier orbital to the substituents can increase electronic couplings between neighboring molecules. This leads to improved charge-transfer rates and, hence, larger charge-mobility. We therefore suggest using the mesomeric effect (as opposed to the inductive effect) when attaching substituents to aromatic cores, which is necessary for example in deep blue OLEDs, where the energy levels of a host molecule have to be adjusted to those of the emitter.rnFurthermore, the energy landscape for charges in an amorphous phase cannot be predicted by mesoscopic models because they approximate the realistic morphology by a lattice and represent molecular charge distributions in a multipole expansion. The microscopic approach shows that a polarization-induced stabilization of a molecule in its charged and neutral states can lead to large shifts, broadening, and traps in the distribution of charge energies. These results are especially important for multi-component systems (the emission layer of an OLED or the donor-acceptor interface of an organic solar cell), if the change in polarizability upon charging (or excitation in case of energy transport) is different for the components. Thus, the polarizability change upon charging or excitation should be added to the set of molecular parameters essential for understanding charge and energy transport in organic semiconductors.rnWe also studied charge transport in self-assembled systems, where intermolecular packing motives induced by side chains can increase electronic couplings between molecules. This leads to larger charge mobility, which is essential to improve devices such as organic field effect transistors, where low carrier mobilities limit the switching frequency.rnHowever, it is not sufficient to match the average local molecular order induced by the sidernchains (such as the pitch angle between consecutive molecules in a discotic mesophase) with maxima of the electronic couplings.rnIt is also important to make the corresponding distributions as narrow as possible compared to the window determined by the closest minima of thernelectronic couplings. This is especially important in one-dimensional systems, where charge transport is limited by the smallest electronic couplings.rnThe immediate implication for compound design is that the side chains should assist the self-assemblingrnprocess not only via soft entropic interactions, but also via stronger specific interactions, such as hydrogen bonding.rnrnrnrn

Investigation of the Hygroscopic and Morphological Properties of Atmospheric Aerosols

The first objective of this thesis was to examine the hygroscopic and morphological nature of various substances through the use of an Environmental Scanning Electron Microscope (ESEM). The hygroscopic growth and changes in morphology for pure-component aerosols were studied for particles greater than 2 µm in size. Hygroscopic growth was observed through changes in relative humidity (RH) and hygroscopic growth curves were created. The second objective of this thesis, the hygroscopic growth of multi-component aerosol mixtures, was studied using Hygroscopic Tandem Differential Mobility Analysis(HTDMA). The size distribution for an aerosol stream was determined before and after the stream was subjected to an increase in relative humidity.

Formative Evaluation of the "Time Twisters": A Comic Book Based Obesity Prevention Curriculum for Elementary School Students

Introduction: Obesity is a public health problem, particularly in Hispanic children. Alternative media channels may offer the potential to motivate children to engage in health promoting behaviors. A comic book, “Time Twisters”, was developed to impact screen time use, physical activity, and dietary behavior for elementary school children and evaluated for acceptability and feasibility prior to implementation in a multi-component physical activity intervention. [See PDF for complete abstract]

Physical Activity in Latino Children: Research and Its Implications

Childhood obesity affects children across all ages and genders. However, Latino children and adolescents are at an increased risk, with one out of three Latino children (ages 2-19) being classified as overweight. Physical inactivity is deemed a major factor contributing to the energy imbalance that leads to excess adiposity. The aims of this study are twofold: 1) to present relevant research regarding Latino children’s physical patterns, influences on their physical activity, and interventions designed to promote physical activity and fitness in this population; and 2) to discuss implications derived from this research to help health educators, practitioners, and policy makers increase awareness, and to motivate and enable Latino children to adopt an active lifestyle. Research reveals that Latino children and adolescents are consistently less active than their white counterparts. Latino girls are, in particular, at an increased risk for inactivity. Few studies have investigated the factors that contribute to low levels of physical activity among Latino children. Moreover, few physical activity interventions have involved Latino children. Some of our recent research studies have filled some gaps, including providing information on what physical activities Latino children like, what they intend to do, what they are actually doing, and where and when they do physical activity. Based on our research and review of related literature, we made specific physical activity recommendations for researchers, practitioners, and policy makers. These individual points should be applied and integrated within a broad framework and used in combinations to develop multi-component, coordinated approaches to enhancing physical activity among Latino youth.

Myelination of the right parahippocampal cingulum is associated with physical activity in young healthy adults.

Recent evidence suggests that individual differences in physical activity (PA) may be associated with individual differences in white matter microstructure and with grey matter volume of the hippocampus. Therefore, this study investigated the association between PA and white matter microstructure of pathways connecting to the hippocampus. A total of 33 young, healthy adults underwent magnetic resonance imaging (MRI). High angular resolution diffusion-weighted imaging and multi-component relaxometry MRI scans (multi-component driven equilibrium pulse observation of T1 and T2) were acquired for each participant. Activity levels (AL) of participants were calculated from 72-h actigraphy recordings. Tractography using the damped Richardson Lucy algorithm was used to reconstruct the fornix and bilateral parahippocampal cinguli (PHC). The mean fractional anisotropy (FA) and the myelin water fraction (MWF), a putative marker of myelination, were determined for each pathway. A positive correlation between both AL and FA and between AL and MWF were hypothesized for the three pathways. There was a selective positive correlation between AL and MWF in the right PHC (r = 0.482, p = 0.007). Thus, our results provide initial in vivo evidence for an association between myelination of the right PHC and PA in young healthy adults. Our results suggest that MWF may not only be more specific, but also more sensitive than FA to detect white matter microstructural alterations. If PA was to induce structural plasticity of the right PHC this may contribute to reverse structural alterations of the right PHC in neuropsychiatric disorder with hippocampal pathologies.

Prevalence of depressive symptoms in urban middle and high school Hispanic and African American students

This cross-sectional study examined the prevalence of depressive symptoms in urban Hispanic and African American middle and high school students (N=1,292) using data collected from a multi-component, multi-wave violence and substance use intervention program targeted at a large urban school district in Texas. Chi-square analysis was used to examine differences in race/ethnicity, gender, grade level and whether or not a student had been held back/repeated a grade in school. Univariate and multivariate logistic regression were used to analyze the association between depressive symptoms and demographic variables. Being female and being held back/repeating a grade was significantly associated with depressive symptoms in both univariate and multivariate analyses. Overall 16% of the students reported depressive symptoms; Hispanic youth had a higher prevalence of depressive symptoms (16.8%) than the African American youth (14.8%). Minority females and those who had been held back/repeated a grade reported a prevalence of 19.4% and 21.2%, respectively. Further research is needed to understand why Hispanic youth continue to report a higher prevalence of depressive symptoms than other minorities. Additionally research is required to further explore the association between academic performance and depressive symptoms in urban minorities, specifically the effect of being held back/repeating a grade.^

A space-time analysis of reported shigellosis and salmonellosis cases in Texas from 2000 to 2004

Background. The purpose of this study was to describe the risk factors and demographics of persons with salmonellosis and shigellosis and to investigate both seasonal and spatial variations in the occurrence of these infections in Texas from 2000 to 2004, utilizing time series analyses and the geographic information system digital mapping methods. ^ Methods. Spatial Analysis: MapInfo software was used to map the distribution of age-adjusted rates of reported shigellosis and salmonellosis in Texas from 2000–2004 by zip codes. Census data on above or below poverty level, household income, highest level of educational attainment, race, ethnicity, and urban/rural community status was obtained from the 2000 Decennial Census for each zip code. The zip codes with the upper 10% and lower 10% were compared using t-tests and logistic regression to determine whether there were any potential risk factors. ^ Temporal analysis. Seasonal patterns in the prevalence of infections in Texas from 2000 to 2003 were determined by performing time-series analysis on the numbers of cases of salmonellosis and shigellosis. A linear regression was also performed to assess for trends in the incidence of each disease, along with auto-correlation and multi-component cosinor analysis. ^ Results. Spatial analysis: Analysis by general linear model showed a significant association between infection rates and age, with young children aged less than 5 and those aged 5–9 years having increased risk of infection for both disease conditions. The data demonstrated that those populations with high percentages of people who attained a higher than high school education were less likely to be represented in zip codes with high rates of shigellosis. However, for salmonellosis, logistic regression models indicated that when compared to populations with high percentages of non-high school graduates, having a high school diploma or equivalent increased the odds of having a high rate of infection. ^ Temporal analysis. For shigellosis, multi-component cosinor analyses were used to determine the approximated cosine curve which represented a statistically significant representation of the time series data for all age groups by sex. The shigellosis results show 2 peaks, with a major peak occurring in June and a secondary peak appearing around October. Salmonellosis results showed a single peak and trough in all age groups with the peak occurring in August and the trough occurring in February. ^ Conclusion. The results from this study can be used by public health agencies to determine the timing of public health awareness programs and interventions in order to prevent salmonellosis and shigellosis from occurring. Because young children depend on adults for their meals, it is important to increase the awareness of day-care workers and new parents about modes of transmission and hygienic methods of food preparation and storage. ^

Youth empowerment evaluation to improve afterschool programming

Community-based participatory research necessitates that community members act as partners in decision making and mutual learning and discovery. In the same light, for programs/issues involving youth, youth should be partners in knowledge sharing and evaluation (Checkoway & Richards-Schuster, 2004). This study is a youth-focused empowerment evaluation for the Successful Youth program. Successful Youth is a multi-component youth development after-school program for Latino middle school youth, created with the goal of reducing teen pregnancy. An empowerment evaluation is collaborative and participatory (Balcazar and Harper 2003). The three steps of an empowerment evaluation are: (1) defining mission, (2) taking stock, and (3) planning for the future (Fetterman 2001).^ In a program where youth are developing leadership skills, making choices, and learning how to self reflect and evaluate, the empowerment evaluation could not be more aligned with promoting and enhancing these skills. In addition, an empowerment evaluation is designed to "foster improvement and self-determination" and "build capacity" (Fetterman 2001). Four empowerment groups were conducted with approximately 6-9 Latino 7th grade students per group. All participants were enrolled in the Successful Youth program. Results indicate points where students' perceptions of the program were aligned with the program's mission and where gaps were identified. Students offered recommendations for program improvements. Additionally, students enjoyed expressing their feelings about the program and appreciated that their opinions were valued. Youth recommendations will be brought to program staff; and, where possible, gaps will be addressed. Empowerment evaluations with youth will continue during the duration of the program so that youth involvement and input remains integral in the evaluation and to ascertain whether the program's goals are being met. ^