No description available.

Evaporated films of radioactive sodium chloride have been prepared by direct sublimation onto a water cooled quartz substrate at 10-⁵ mm of mercury. These possess specific surfaces of from 30-100 m²/g and show remarkably high exchange reactivity to chlorine. From kinetic studies using ³⁶Cl incorporated in the solid it has been found that the extent of exchange C follows a fractional power of the time C = at[superscript n] and that the rate is independent of surface area, so that the possibility of the rate controlling step involving diffusion is ruled out. These features had been reported in an earlier study but required confirmation with a wider range of specific surface and a modified procedure to measure surface area before reaction. The major part of the work is designed to elucidate the role of electronic defects in the exchange mechanism from the pressure and temperature dependence of the exchange rate and from the effect of introducing electronic defects by X-irradiation or fluoridation. These latter processes cause the kinetics of the reaction to change completely to a second-order law, and provide strong evidence to support an earlier tentative suggestion that electronic defects are involved in the reaction, and that a process of adsorption of a chlorine molecule into a pair of defects is important. Detailed mechanisms are proposed for both the power law and the second-order reactions, largely on the basis of the pressure dependence. Both mechanisms use two species of electronic defect, corresponding to Seitz's models for V₂ and V₄ centres, and the "power law" mechanism requires a transition complex between the two defects. Measurements by X-ray diffraction on the particle size in the evaporated films has shown them to be in the range 250-500 Å, and an estimate of the strain from the same results suggests that roughly one dislocation per particle is present. / Science, Faculty of / Chemistry, Department of / Graduate

The Open Web Application Security Project identifies that the number one vulnerability in mobile applications is the misuse of platform-provided security mechanisms. This means that platforms like iOS and Android, which now account for 99.8\% of the mobile phone market, are providing mechanisms that are consistently being used in an incorrect manner. This statistic shines a spotlight onto both platforms. Why is it that so many people are misusing platform provided security mechanisms? And is it the platform’s fault? The supposition of this paper is that both iOS and Android are not creating usable security mechanisms. This paper is meant to be a direct response to the number one spot on the OWASP Top Ten Mobile Vulnerabilities list. As a result, our primary goal is to identify whether or not iOS and Android are creating usable security mechanisms. To do this we first proposed an evaluation framework that is tailored to evaluate the usability of mobile device security mechanisms. Then we used it to evaluate seven of the most important and therefore most popular security mechanisms provided by iOS and Android. Through this evaluation we not only hope to develop a clear landscape of overall mobile security mechanism usability, but we also hope to compare the usability across the two platforms. Overall, it was found that both platforms adequately supported the more popular security mechanisms like key storage and HTTPS. Whereas support for some of the more low-level mechanisms, like encryption and MACs, were often neglected. Such neglect could be seen in a number of different ways; however, the most common neglect came in the form of old documentation, or APIs that are long over do for a rebuild or increased abstraction. Furthermore, both platforms barely addressed the testing of implementations, despite the fact that testing is arguably the most important part of the software development cycle. Both iOS and Android seldom gave the developer any guidance on verifying the functionality of their implementations.

The selective catalytic reduction (SCR) of NO_X (x = 1,2) using Cu-exchanged zeolites is used commercially for the abatement of NO_X from on-road lean-burn diesel engines. At the low exhaust temperatures during cold-start and idle operation (<523 K), the SCR reaction proceeds via a Cu²⁺/Cu⁺ redox cycle of NH₃-solvated and mobilized Cu ions. Reduction of Cu²⁺ species proceeds via NO-assisted reduction of isolated NH₃-solvated Cu²⁺ ions. To complete Cu⁺ to Cu²⁺ oxidation, two [Cu(NH₃)₂]⁺ species react together with O₂ to form a dimeric O₂-bridged Cu²⁺ species that is subsequently reduced by NO and NH₃ to complete the SCR catalytic turnover. NH₃-solvated Cu ion species are nominally isolated under <i>ex-situ</i> conditions, however, motivating the critical research question studied in this work regarding how Cu ion mobility and dynamic interconversion of mononuclear and binuclear active sites facilitate SCR chemistry. In particular, this work focuses on understanding how active site proximity, zeolite pore connectivity and dimensionality, and catalyst poisons impact the number and reactivity of active Cu sites.<br> Steady-state SCR kinetics (473 K) measured at fixed gas conditions (10 kPa O₂) on a series of Cu-chabazite (CHA) zeolites with varied density of isolated Cu ions (0.078-0.35 Cu per 10³ ų) exhibit non-single site behavior because of changes in the kinetic relevance of Cu⁺ oxidation and Cu²⁺ reduction half-cycles, and the non-mean field nature of the Cu⁺ oxidation process. Measurement of SCR rates at dioxygen pressures (1-60 kPa O₂) far removed from typical operating conditions (3-17 kPa O₂) allows isolating the kinetic behavior under primarily Cu⁺ oxidation-limited and Cu²⁺ reduction-limited conditions, and estimating rate parameters for these two regimes by regressing SCR rates as a function of O2 pressure to an empirical Langmuirian rate expression. Apparent rate constants that are first-order in O₂ (k_first) increase systematically with Cu density, consistent with the dual-site Cu⁺ oxidation mechanism. Apparent rate constants that are zero-order in O2 (k_zero) show a weak dependence on Cu density, similar to the fraction of Cu that can be oxidized by O₂ at 473 K in transient experiments, suggesting that changes in k_zero reflect changes in the fraction of active Cu given the single-site nature of Cu²⁺ reduction mechanisms. The measured apparent activation energy in the Cu⁺ oxidation limit (E_app,first) increases systematically with Cu density, highlighting the non-mean field nature of Cu⁺ oxidation over the range of Cu densities studied. The measured apparent activation energies in the Cu²⁺ reduction limit are constant above a threshold Cu density (0.17 Cu per 10³ ų), consistent with mean-field behavior, but begin to deviate at lower densities (0.084-0.10 Cu per 10³ ų).<br> A series of Cu-zeolites with 2D (LEV, FER) and 1D (MOR) pore connectivity were synthesized to quantify how the framework topology and pore structure influences the mobility and reactivity of Cu ions during SCR. When compared to Cu-CHA, a 3D pore structure, values of k_first and k_zero (per total Cu) were several factors lower on the 2D and 1D zeolites, indicating that decreasing the effective volumetric footprint of Cu ions during SCR decreases both the rate of dual-site Cu⁺ oxidation and the fraction of Cu⁺ that oxidizes. When compared to other 3D double-six membered ring (d6r) zeolites with different pore shape (AEI) and size (AFX), rates (per total Cu) were generally a factor of 1.5 to 2 times higher on Cu-CHA, indicating that the open pore structure of cylindrical cages in CHA are favorable for low-temperature SCR reactivity.<br> The arrangement and density of framework Al atoms in CHA influences low-temperature SCR, as the framework Al atoms mediate Cu ion mobility and the arrangement of Al in the framework determines the chemical identity of the Cu active site precursors as either [CuOH]⁺ exchanged at an isolated framework Al center or Cu²⁺ exchanged at paired framework Al in a six-membered ring (6-MR). Synthesis of CHA zeolites with mixtures of Na⁺ and TMAda⁺ provides a strategy to alter the amount of Al centers in 6-MR paired configurations, because Na+ co-occludes in 6-MR voids adjacent to TMAda⁺ occluded within the cha cage. In contrast, synthesis of CHA zeolites with mixtures of K⁺ and TMAda⁺ results in primarily 6-MR isolated Al configurations because K⁺ cations displace TMAda⁺ from residing in cha cages. Thus, the use of different mixtures of organic and inorganic structure directing agents (SDAs) provide routes to synthesize CHA zeolites that favor the formation of either [CuOH]⁺ or Cu²⁺ species. The Cu speciation influences both hydrothermal stability and resistance to sulfur poisoning. SO₂ is a catalyst poison ubiquitous in automotive exhaust and is found to bind to [CuOH]⁺ sites more strongly than Cu²⁺ sites, both before and after high-temperature de-sulfation treatments. <br> Together, these findings reveal several of the important structural and active site requirements for low-temperature NO_X SCR with NH₃ on Cu-zeolites. The non-mean field nature of the SCR redox cycle on Cu²⁺/Cu⁺ ion sites, and the requirement for Cu ions to be located in proximal and accessible locations of zeolite void spaces becomes more favorable in 3D highly connected pore structures, highlighting a primary reason why low-temperature SCR rates (per Cu) are higher on Cu-CHA than on other Cu-zeolites. The synthetic procedures presented here to influence the Al arrangement in CHA zeolites provide new strategies to alter the speciation and density of isolated Cu ion sites, even among Cu-CHA zeolites of nominally identical elemental composition, which have implications for the stability and resistance to poisons of the catalyst under realistic operating conditions. Together, synthetic strategies to manipulate the proximity of active sites, methods to quantify transient and steady-state kinetics, and <i>in situ</i> and <i>operando</i> characterization are invaluable tools to study and understand the non-mean field dynamic interconversion of isolated and multinuclear sites during low-temperature SCR catalysis.<br>

This study had two major objectives; firstly to test the hypothesis of ongoing competition for seeds between small rodents and harvester ants, Pogonomyrmex occidental is, in a cold desert ecosystem; secondly to elucidate how seed abundance and shrub cover influence the distribution and abundance of deer mice, Peromyscus maniculatus. The study area was a sagebrush (Artemisia tridentata) dominated shrubsteppe in southwestern Wyoming. Responses of the small mammal community to ant removal and food addition were assessed on replicated study plots between September 1981 and September 1983. Food addition and shrub removal manipulations were continued from September 1983 to August 1984. Rodent populations were sampled by live-trapping. Movements of 40 deermice were followed by radiotracking during the winter, spring and summer of 1983-84. Ant removal elicited little response from the rodent community, although seed preference trials with native seeds in the field indicated considerable overlap in seed use. concluded that competition was not a factor affecting small rodents during the period of this study, although the area cleared of ants may not have been sufficiently large to produce a response detectable by trapping. Seed addition resulted in increased deermouse population size, prolonged breeding, decreased winter (but not summer) home range sizes, and during periods of low density, increased grid fidelity. High fall densities were followed by a classical spring decline with associated female sex ratio skew and severe injuries to both sexes. Concluded that deermice were food limited only to the point where social interactions during the breeding season limited maximum densities. The absence of shrubs prevented winter use of the 1.25 ha cleared area by deermice. At this time on the non-cleared plots shrubs were used to support nests, as foraging sites and as a means of access to the snow surface. During summer the area cleared of shrubs provided attractive foraging habitat, but most nest sites were still located within shrub cover around the edge. An important corollary of the radio tracking was the illustration of the large home range sizes of deermice in relation to the size of the 0.7 ha trapping grids. The implications of trapping bias affecting population fluctuations and measurement of other demographic parameters from trapping studies are discussed.

Indiana University-Purdue University Indianapolis (IUPUI) / Little research has explored the degree to which specific intervention components predict improved health outcomes for cancer patients and their family caregivers. The present study examined relations of intervention components (i.e., coping skills) to symptoms in a telephone symptom management (TSM) intervention delivered concurrently to symptomatic lung cancer patients and their family caregivers. Guided by Social Cognitive Theory (SCT) and cognitive behavioral therapy (CBT) frameworks, patient-caregiver dyads were taught coping skills including: a mindfulness exercise (i.e., noticing sounds and thoughts), pursed lips breathing, guided imagery, cognitive restructuring, and assertive communication. Symptom measures were administered at baseline and 2 and 6 weeks post-intervention. The measures assessed patient and caregiver depressive and anxiety symptoms as well as patient pain severity, distress related to breathlessness, and fatigue interference. Data were examined from patient-caregiver dyads enrolled in TSM (N = 51 dyads). Patients and caregivers were predominantly female (55% and 73%, respectively) and Caucasian (87%). The average patient was 63 years of age (SD = 8) and the average caregiver was 56 years of age (SD = 14). Seven autoregressive panel models tested relations of coping skills to symptoms. All models had at least adequate fit to the data (χ2 ps > 0.05, RMSEA values < 0.06). For patients, more assertive communication practice during the intervention was related to less pain severity, fatigue interference, and depressive and anxiety symptoms at 6 weeks post-intervention. Additionally, more guided imagery practice during the intervention was related to less fatigue interference and anxiety at 6 weeks post-intervention. In contrast, more cognitive restructuring practice during the intervention was related to more distress related to breathlessness and depressive and anxiety symptoms at 6 weeks post-intervention. Similarly, more practice of a mindfulness exercise during the intervention was related to more fatigue interference and anxiety at 6 weeks post-intervention. For caregivers, more guided imagery practice was related to more anxiety at 2 weeks post-intervention. All other pathways from coping skills to symptoms at 2 and 6 weeks post-intervention were non-significant for both patients and caregivers. Findings suggest intervention effectiveness may have been reduced by competing effects of certain coping skills. For lung cancer patients, future studies should consider focusing on assertive communication and guided imagery, as these two coping skills were most consistently associated with reduced symptoms. However, more studies are needed to better understand these findings and particular caution should be used when applying CBT-based interventions that have not been validated in lung cancer populations.

No description available.

No description available.

No description available.

No description available.