Scaling analysis of the screening length in concentrated electrolytes

The interaction between charged objects in an electrolyte solution is a fundamental question in soft matter physics. It is well-known that the electrostatic contribution to the interaction energy decays exponentially with object separation. Recent measurements reveal that, contrary to the conventional wisdom given by classic Poisson-Boltzmann theory, the decay length increases with ion concentration for concentrated electrolytes and can be an order of magnitude larger than the ion diameter in ionic liquids. We derive a simple scaling theory that explains this anomalous dependence of the decay length on ion concentration. Our theory successfully collapses the decay lengths of a wide class of salts onto a single curve. A novel prediction of our theory is that the decay length increases linearly with the Bjerrum length, which we experimentally verify by surface force measurements. Moreover, we quantitatively relate the measured decay length to classic measurements of the activity coefficient in concentrated electrolytes, thus showing that the measured decay length is indeed a bulk property of the concentrated electrolyte as well as contributing a mechanistic insight into empirical activity coefficients.Comment: To appear in Physical Review Letter

Prediction of force coefficients for labyrinth seals

The development of a linear model for the prediction of labyrinth seal forces and on its comparison to available stiffness data is presented. A discussion of the relevance of fluid damping forces and the preliminary stages of a program to obtain data on these forces are examined. Fluid-dynamic forces arising from nonuniform pressure patterns in labyrinth seal glands are known to be potentially destablizing in high power turbomachinery. A well documented case in point is that of the space Shuttle Main Engine turbopumps. Seal forces are also an important factor for the stability of shrouded turbines, acting in that case in conjunction with the effects of blade-tip clearance variations

Framing the mass shooter James Eagan Holmes: serious mental illness and gun violence

2019 Fall.Includes bibliographical references.This study examined the framing of serious mental illness (SMI) and gun violence focused on the single case of the 2012 Aurora Theater Shooting perpetrated by James Eagan Holmes. At the time, it was the most devastating mass shooting in U.S. history with 58 injured and 12 killed. The overarching question guiding the study asked how online news stories about the Aurora Theater Shooting frame serious mental illness and mass shootings. A content analysis was conducted on four news websites, two local publications and two national publications. This was designed to detect geographical trends in reporting. Key findings were a lack of causal attribution to SMI or any other cause, which disagreed with former research that found SMI as a commonly-attributed cause to gun violence after mass shootings in news media coverage. Gun restriction policy was found to be more prevalent in national news than in local news suggesting differences in coverage by geographic location. SMI and gun restriction policy proposals did not appear together in stories often pointing to a split in individual- or societal-level responsibility. A final finding was a singular mental health professional source utilized in the 187-story sample suggesting a lack of mental health experts in crime reporting after a mass shooting. Further research could explore the crime beat reporters' source-gathering habits particularly when dealing with crime purveyed by people with SMI as well as a study assessing mental health professionals' views on being used as a source in crime news reporting

Con el Nopal en la Frente

This MFA thesis addresses work completed and presented in a thesis exhibition at West Virginia University as well as significant influences and events that relate to process and concept. Con el Nopal en la Frente consists of several ceramic sculptures that reference elements of a landscape typical in southwest Texas. Using symbols and phrases that are common along the Texas-Mexico border, this thesis and supporting exhibition investigates contemporary expressions of xenophobia. During my years away from home, the presence of microaggressions and racist remarks, said both intentionally and unintentionally, was common. This was new to me. Often times, those saying these comments did not understand how and why such remarks are considered insulting or bigoted. The goal of this work is to offer the opportunity for viewers to contemplate how their remarks, no matter the intent, are pointed implications of foreignness

Evaluation of Carbonyl Collection Methods in Electronic Cigarette Aerosol

Popularity of electronic cigarettes (e-cigarettes) has been growing rapidly. Harmful compounds have been reported in e-cigarettes aerosols including carbonyls, such as the human carcinogens formaldehyde and acetaldehyde. Current standard method testing e-cigarette carbonyl emissions were adopted from conventional cigarette testing method. However, while carbonyls in conventional cigarette smoke found mostly in gas phase, it was reported that a large fraction of carbonyl compounds in e-cigarette aerosols could be in the particle phase. Since standard carbonyl testing methods (i.e., impinger method) are not designed to quantitatively capture particulates, there are discrepancies in e-cigarette carbonyl emissions reported by studies using different sampling methods. This study assesses carbonyl collection methods for the emissions from different e-cigarette devices to provide a standardized testing method.To address the gas and particle-bound carbonyl discrepancy, the three most frequently used methods were tested: 2,4- Dinitrophenyl hydrazine (DNPH) silica impregnated cartridge (C), DNPH- coated glass fiber filter (DF), and impinger (I). Glass fiber filter (GF) was also used to estimate the particle-bound carbonyl fraction. The sampling media were combined as follows: I-I, GF-I-I, C, DF-C, and GF-C. For sample collection, two e-cigarettes ‘pod’ (i.e., JUUL) and ‘mod’ type at different flows were used. Collected samples were analyzed using high-performance liquid chromatography with photodiode array detection (HPLC-PDA Arc 2690 with a 2998 photodiode array detector, Waters, MA, USA). Carbonyl emissions varied between methods at different flows. For both devices, the highest emissions were measured with C and DF-C. I-I measured similar emissions for JUUL, but significantly lower for mod. For example, mod formaldehyde emissions measured with C were 0.11 ± 0.08 and 0.12 ± 0.08 µg/puff for 1 liter per minute (LPM) and 1.5 LPM, respectively. The I-I method, however, indicated 0.02 ± 0.01 and 0.03 ± 0.01 µg/puff, 33% and 40% lower than C at the same respective conditions. This discrepancy between the C and I-I methods generally followed the amount of liquid aerosol produced by the device. While C and DF-C were similar for formaldehyde, C indicated JUUL acetaldehyde emissions that were 46% lower than those measured with DF-C, while for mod they were close to each other. This could be due to the larger particle-bound fraction of acetaldehyde and the smaller particles produced by JUUL that are apparently less effectively caught by the cartridge relative to the larger mod particles. For total aerosol –hence gas and particle –, the C and DF-C provides the best approach. In conclusion, it has been shown that the standard method (i.e., I-I) underestimates the carbonyl emissions because of its design to capture gas phase in the e-cigarette aerosol. However, as different studies have shown and as the e-cigarette market increases and new –bigger and powerful – products are developed, the necessity for refinement and advancement arises. Because of these reasons, it is recommended that the standard method is not used for e-cigarette aerosol sampling

Improved Bounds on Information Dissemination by Manhattan Random Waypoint Model

With the popularity of portable wireless devices it is important to model and predict how information or contagions spread by natural human mobility -- for understanding the spreading of deadly infectious diseases and for improving delay tolerant communication schemes. Formally, we model this problem by considering $M$ moving agents, where each agent initially carries a \emph{distinct} bit of information. When two agents are at the same location or in close proximity to one another, they share all their information with each other. We would like to know the time it takes until all bits of information reach all agents, called the \textit{flood time}, and how it depends on the way agents move, the size and shape of the network and the number of agents moving in the network. We provide rigorous analysis for the \MRWP model (which takes paths with minimum number of turns), a convenient model used previously to analyze mobile agents, and find that with high probability the flood time is bounded by $O\big(N\log M\lceil(N/M) \log(NM)\rceil\big)$, where $M$ agents move on an $N\times N$ grid. In addition to extensive simulations, we use a data set of taxi trajectories to show that our method can successfully predict flood times in both experimental settings and the real world.Comment: 10 pages, ACM SIGSPATIAL 2018, Seattle, U

Phosphorus-containing sulfonated polyimides for proton exchange membranes

Synthesis and characterization of the novel sulfonated BAPPO monomer and its use in the synthesis of a new phosphine oxide-based sulfonated polyimide are described. BTDA, 6FDA, and DDS were used as monomers in the polyimide synthesis. Sulfonated polyimide membranes were obtained by a solution thermal imidization method. The thermal behavior of the polymers was investigated by DSC and TGA. The morphological structure of the membranes was investigated by tapping-mode AFM. The proton conductivities of the sulfonated polyimide increased regularly as a function of sulfonated diamine content. The conductivities are good compared to typical proton exchange membranes

Spin Hall torque magnetometry of Dzyaloshinskii domain walls

Current-induced domain wall motion in the presence of the Dzyaloshinskii-Moriya interaction (DMI) is experimentally and theoretically investigated in heavy-metal/ferromagnet bilayers. The angular dependence of the current-induced torque and the magnetization structure of Dzyaloshinskii domain walls are described and quantified simultaneously in the presence of in-plane fields. We show that the DMI strength depends strongly on the heavy metal, varying by a factor of 20 between Ta and Pa, and that strong DMI leads to wall distortions not seen in conventional materials. These findings provide essential insights for understanding and exploiting chiral magnetism for emerging spintronics applications