This research effort investigated the influence of confinement on the physical aging behavior of thin and ultrathin glassy polymer membranes. Membrane permeability changes with time due to physical aging, and for reasons not completely understood, the rate of permeability change can become orders of magnitude faster in films thinner than one micron. Special experimental techniques were developed to enable the study of free standing, ultrathin glassy polymer films using gas permeability measurements. The gas transport properties and physical aging behavior of free-standing glassy polysulfone (PSF) and Matrimid® films from 18-550 nm thick are presented. Physical aging persists in glassy films approaching the length scale of individual polymer coils. The membranes exhibited significant reductions in gas permeability and increases in selectivity with aging time. Additionally, the influence of physical aging on the free volume profile in thin PSF films was investigated using variable energy positron annihilation lifetimespectroscopy (PALS). The films exhibited decreasing o-Ps lifetime during physical aging, while o-Ps intensity remained constant. The o-Ps lifetime was reduced at lower implantation energies, indicating smaller free volume elements near the film surface. Thin films aged dramatically faster than bulk PSF and the PALS results agree favorably to behavior tracked by gas permeability measurements. The physical aging behavior of ultrathin films with different previous histories was also studied. The state of these materials was modulated by various conditioning treatments. Regardless of the previous history, the nature of the aging response was consistent with the aging behavior of an untreated film that was freshly quenched from above Tg, i.e., permeability decreased and pure gas selectivity increased with aging time. However, the extent of aging-induced changes in transport properties of these materials depended strongly on previous history. The properties of these ultrathin films deviate dramatically from bulk behavior, and the nature of these deviations is consistent with enhanced mobility and reduced Tg in ultrathin films, which allows them to reach a lower free volume state more quickly than bulk material. The Struik physical aging model was extended to account for the influence of film thickness on aging, and was shown to accurately describe the experimental data. / text

Physical scaling limits of microelectronic devices and the need to improve electrical performance have driven significant research and development into 3D architecture. The development of die stacks in first level packaging is one of the more viable short-term options for improved performance. Placement of memory die above or below processors in a traditional flip chip C4 package with through-silicon vias (TSVs) has significant benefits in reducing data and power transmission paths. However, with the electrical performance benefits come great thermal and mechanical challenges. There are two key objectives for this work. The first is understanding of the die-die interface resistance, R[subscript dd], composed of the back end of line (BEOL) layers and micro-C4 interconnects. The interfacial resistance between BEOL material layers, the impact of TSVs and the impact of strain on R[subscript dd] are subtopics. The second key objective is the understanding of package thermal and mechanical behavior under operating conditions, such as local thermal disturbances. To date, these topics have not been adequately addressed in the literature. It is found that R[subscript dd] can be affected by TSVs, and that the interfacial contributions predicted by theoretical sub-continuum models can be significantly different than measurements. Using validated finite element models, the significance of the power distribution and R[subscript dd] on the temporal responses of 2D vs. 3D packages is highlighted. The results suggest local thermal hotspots can greatly exacerbate the thermal penalty due to the R[subscript dd] and that no peaks in stress arise in the transient period from power on to power off. / text

We study the quadratic form induced by the Bezoutian of two polynomials p and q, considering four problems. First, over R, in the separable case we count the number of configurations of real roots of p and q for which the Bezoutian has a fixed signature. Second, over Qp we develop a formula for the Hasse invariant of the Bezoutian. Third, we formulate a conjecture for the behavior of the Bezoutian in the non separable case, and offer a proof over R. We wrote a Pari code to test it over Qp and Q and found no counterexamples. Fourth, we state and prove a theorem that we hope will help prove the conjecture in the near future. / text

Although silicon (Si) nanostructures exhibit size dependent light emission, which can be attributed to quantum confinement, the role of surface passivation is not yet fully understood. This understanding is central to the development of nanocrystal-based detectors. This study investigated the growth, surface chemistry, passivation with deuterium (D2), ammonia (ND3) and diborane (B2D6) and the resulting optical properties of Si nanostructures. Si nanocrystals less than 6 nm in diameter are grown on SiO2 surfaces in an ultra high vacuum chamber using hot-wire chemical vapor deposition and the as grown surfaces are exposed to atomic deuterium. Temperature programmed desorption (TPD) spectra show that that the nanocrystals surfaces are covered by a mix of monodeuteride, dideuteride and trideuteride species. The manner of filling of the deuteride states on nanocrystals differs from that for extended surfaces as the formation of the dideuteride and trideuteride species is facilitated by the curvature of the nanocrystal. No photoluminescence (PL) is observed from the as grown unpassivated nanocrystals. As the deuterium dose is increased, the PL intensity also begins to increase. This can be associated with increasing amounts of mono-, di- and trideuteride species on the nanocrystal surface, which results in better passivation of the dangling bonds and relaxing of the reconstructed surface. At high deuterium doses, the surface structure breaks down and amorphization of the top layer of the nanocrystal takes place. Amorphization reduces the PL intensity. Finally, as the nanocrystal size is varied, the PL peak shifts, which is characteristic of quantum confinement. The dangling bonds and the reconstructed bonds at the NC surface are also passivated and transformed with D and NDx by using deuterated ammonia (ND3), which is predissociated over a hot tungsten filament prior to adsorption. At low hot wire ND3 doses PL emission is observed at 1000 nm corresponding to reconstructed surface bonds capped by predominantly monodeuteride and Si-ND2 species. As the hot wire ND3 dose is increased, di- and trideuteride species form and intense PL is observed around 800 nm that does not shift with NC size and is associated with defect levels resulting from NDx insertion into the strained Si-Si bonds forming Si2=ND. The PL intensity at 800 nm increases as the ND3 dose is increased and the intensity increase is correlated to increasing concentrations of deuterides. At extremely high ND3 doses PL intensity decreases due to amorphization of the NC surface. In separate experiments, Si NCs were subjected to dissociative (thermal) exposures of ammonia followed by exposures to atomic deuterium. These NCs exhibited size dependent PL and this can be attributed to the prevention of the formation of Si2=ND species. Finally, deuterium-passivated Si NCs are exposed to BDx radicals formed by dissociating deuterated diborane (B2D6) over a hot tungsten filament and photoluminescence quenching is observed. Temperature programmed desorption spectra reveal the presence of low temperature peaks, which can be attributed to deuterium desorption from surface Si atoms bonded to subsurface boron atoms. The subsurface boron likely enhances nonradiative Auger recombination. / text

Research was compiled in regards to the effect of various changes in the development and fabrication of the ultracapcitor. The binder was changed from Teflon to a mix of Teflon and Nafion. Results demonstrated that an increase in capacitance was seen in the ultracapcitor and is may be attributed to the structure of Nafion. Furthermore water soluble graphene, graphene oxide, and ionic liquid graphene was tested in order to determine the effects of those alterations on the overall capacitance. / text

Heeding the call by Firth and Wagner (1997) for a re-analysis of some of the “facts” of modern second language (L2) learning theory and research, the goals of this present study are to determine if: (1) informal conversations between a NS of English (NES) learning Spanish and a NS of Spanish (NSS) learning English reveal insight regarding the natural use and interaction of the first (L1) and the target language (TL); (2) informal L2 conversations in which the L1 is permitted present opportunities for L2 teaching, learning or socialization; and (3) provided that evidence of possible opportunities for L2 teaching, learning or socialization is found, does this indicate a need for permitting both informal talk and the use of the L1 in the L2 learning context. It was hypothesized that in informal conversations, learners would demonstrate intuitive approaches to L2 learning, teaching and socialization, and that observations of these phenomena could help guide research and pedagogy regarding the L2 learning context. It was also hypothesized that informal language exchanges would demonstrate that when left to intuition, participants would provide quality NS input and modified NNS output for their partners as they alternated between L1 and L2 and between the roles of language teacher and language learner. Previous studies have shown that the ability to control the language being used and the topic being discussed allows learners to access knowledge and linguistic structures that enable them to feel more comfortable using the L2 and less anxious about interacting in L2 conversations (Auerbach 1993; Tomlinson 2001; Lantolf and Thorne 2007). The design of this study was intended to address the concept of bi-directional informal discourse in learner/expert learner/expert pairs (i.e., participants who are each learners of their partners’ L1) and the informal exchange of two languages in the L2 learning context. Although the importance of language learning and use in context have been described since the early 20th century in the work of Vygotsky, and the phenomenon of participant orientation and role-switching has also been examined in recent years, there have been relatively few studies that have looked at the nexus of social talk and reciprocal teaching by pairs of learner/experts as this context interacts with the use of the L1 and the L2 in an informal communication event. Data for the study were obtained from audio recordings of four conversations between pairs of native Spanish speakers learning English and native English speakers learning Spanish with the goal of determining what the participants would teach to one other through the use of informal, unstructured conversation using both the L1 & the L2. In addition, all of the participants completed an exit interview questionnaire on their experience with the interaction as well as their general opinions regarding language learning. The data showed that 7 out of 8 participants did teach (intentionally or unintentionally) both linguistic and extra-linguistic information from their L1 to their partners, and that in all pairs a local set of rules regarding the use of the L1was established (including the pair in which no English was used). The pairs modeled an intuitive use of the L1 demonstrating the ability of the L1 both to bridge conversational gaps and to enable teaching and socialization in the L2. The data also show how the participants built a community of practice by setting and changing the language used, requesting explicit feedback or evaluation from their partners, bonding over language learning struggles, as well the linguistic and extra-linguistic information that the participants provided for their partners. The results of the study indicate potential benefits both for the use of the L1 in the L2 learning context, and for allowing learners to teach from their own L1 while learning the L2 in informal conversations. However, the recordings and the exit interviews also show some potential problems for implementation (e.g., the possibility that a conversation may be carried out in just one language). The conclusions present implications and applications for the study, such as the establishment of language exchange programs as a supplement to traditional L2 classes, as well as the limitations of the study and suggestions for further research. / text

Polythiophenes have shown potential as inexpensive organic semiconductors because of their charge mobility properties. Small changes in structures can change the electronic and optical properties. Because oligothiophenes demonstrate the same electronic properties, have better solubility, and are easier to purify without defects, oligothiophenes are used as models for the polythiophenes. X-ray diffraction is an accepted method for studying the structure and arrangement of atoms in oligothiophenes; however, XRD requires crystalline solids for analysis. Obtaining suitable crystals can be difficult. In this paper, two crystallization techniques, vapor diffusion and zone sublimation, and the results are discussed. Raman spectroscopy, a type of vibrational spectroscopy, will give information about the structure of a molecule and can act as the molecular fingerprint of the molecule. Raman spectroscopy does not require crystalline solids and provides a relatively fast analysis. If the Willets lab can characterize the oligothiophenes by Raman spectroscopy, demonstrate distinguishable spectra for the different morphologies, and correlate this to the X-ray diffraction data, Raman spectroscopy will be an easier and faster means for analyzing the oligothiophenes. / text

The purpose of this study was to analyze the effects of audience response systems on the secondary classroom. High school students (n=61) participated in one of three groups: (1) a control group, which heard traditional lectures with verbal questions only, (2) a clicker group, which had questions displayed and used clickers to answer, and (3) a questions only group, which had questions displayed but used slips of paper to answer the question. ANOVA was used to analyze various sources of data, including: test scores, post-test scores, and others, and it was found that there was no statistical difference between the control and two treatment groups. A focus group (n=4) was held to gather qualitative data. Students in the focus group indicated that they enjoyed using clickers for various reasons. Focus group participants indicated that clickers allowed for increased interaction between students and teacher and between students, the graphs allowed students to understand how they performed compared to the class, and gave opportunities for competition. More data needs to be collected on the use of clickers and how the discussion they foster might lead to increased learning. / text

Nuclear power waste contains radioactive isotopes with long half lives and the problem lies in the fact that the lanthanides and actinides must be separated before the nuclear waste can be reprocessed. Transuranic Extraction (TRUEX), a liquid-liquid extraction method, has been developed but fails to separate the lanthanide and actinides and creates large volumes of liquid waste. It has been shown that attaching three CMPO (carbamoyl phosphine oxide) ligands used in the TRUEX process to a calixarene increases the separation and extraction efficiency of the system. The research goal is to attach the CMPO ligand to a polymer to make a membrane to be used in nuclear waste remediation. The triblock polymer system has been designed to have a cross-linking group to create the membrane structure, a solubilizing group to improve the flow of aqueous media through the membrane, and the CMPO ligand to chelate actinides. This paper describes the design of the polymer, its synthesis, and my research data. / text

The research project, The Enzymatic Synthesis of CoA Derivatives Using a New ATP Regeneration System, describes the multiple lab trials conducted to develop an ATP regeneration system using various concentrations of specific substrates and the two enzymes MatB and PrpE. Reactions were combined using different concentrations of ADP, the addition or removal of ADK (adenylate kinase), and the substitution of either MatB or PrpE. Further reactions were combined using trans-crotonyl, trifluoroacetic acid, butyric acid, acetic acid, and creatine phosphokinase. This report also includes the methods used and analysis of the different chromatographs of each sample tested. / text