On the Frontlines of Todays Cities: Trauma, Challenges and Solutions

Local officials work at the level of government closest to the people, and with that comes great responsibility and great challenge. While public officials at the state and federal level have faced harassment and threats for decades, this trend has now made its way to cities, with local leaders on the frontlines of these challenges. Driven by increasing polarization, the spread of mis- and disinformation and the growing influence and power of social media, local officials face everything from racist, homophobic attacks online to city council meetings that devolve into screaming matches. The COVID-19 pandemic, racial reckoning and other recent national crises pushed many things to the extreme and threats and harassment against local leaders are no exception. While a certain amount of disagreement is a healthy part of a functioning democracy, civil discourse in America has been increasingly in decline. Eighty-seven percent of surveyed local officials have noticed an increase in levels of harassment, threats and violence during their time in office.While more than 8 in 10 surveyed local officials have experienced some form of harassment, threats and violence, fewer than half work in an office with a strategy to handle these incidents. This report sheds light on the impact felt by local officials and their communities across the country and offers a three-pronged approach to help keep them safe from threats, while maintaining their mental and physical wellbeing

Die Quellen des Rigischen Stadtrechts bis zum Jahr 1673

 ABSTRACT This master thesis defines a new concept – Math Videos on the Net. The term refers to short, educational videos of mathematics that are freely available on the internet. The videos are designed to offer a complement to other course material for a specific element of a specific math course and are directed to the target group of students studying the latter. Within this work, Math Videos on the Net have been created for the Swedish upper secondary school courses Matematik 1b and 1c. The study aims to describe, analyze and interpret whether, and if so, how Math Videos on the Net can help support the work of teachers and students’ development of knowledge in the first mathematics course of the Swedish upper secondary school. Teachers are asked to test selected Math Videos on the Net together with their students in the course Matematik 1b. Collected results from the test are analyzed and interpreted based on previous research of Information and Communication Technology, ICT, in education as well as educational theories. The study shows that many students believe that their mathematical knowledge increases as a result of math videos being included in the tuition. When the videos are used both in and outside the classroom, many students in particular believes that they get more out of teaching. The weakest performing students from environments with low socioeconomic status do however not appear to benefit from these positive effects. In addition, the study indicates that the teacher’s use of the videos play a big role when it comes to how Math Videos on the Net can support students’ development of knowledge. Keywords: Mathematics teaching and learning, ICT in education, Open Educational Resources (OER), Math Videos on the NetI detta examensarbete definieras ett nytt begrepp – matteklipp på nätet. Med begreppet menas korta, undervisande videoklipp behandlande matematik som finns gratis tillgängliga på internet. Klippen syftar till att utgöra ett komplement till övrigt kursmaterial för ett specifikt moment av en specifik matematikkurs och är riktade till målgruppen elever studerande den senare. Inom ramen för arbetet har matteklipp på nätet skapats för gymnasieskolans kurser matematik 1b och 1c. Syftet med studien är att beskriva, analysera och tolka om och i så fall hur matteklipp på nätet kan bidra till att stödja lärares arbete och elevers kunskapsutveckling i den nya gymnasieskolans (Gy 2011) första matematikkurs. Undersökningen genomförs genom att matematiklärare testar utvalda matteklipp på nätet tillsammans med sina elever i kursen matematik 1b. Insamlade resultat analyseras och tolkas utifrån tidigare forskning om informations- och kommunikationsteknik, IKT, i undervisningen samt pedagogiska och didaktiska teorier. Studien visar att många elever anser att deras matematikkunskaper ökar som en effekt av att matteklippen inkluderas i undervisningen. När matteklippen används såväl i som utanför klassrummet anser flera elever att de får ut mer av undervisningen. De svagast presterande eleverna från miljöer med låg socioekonomisk status tycks dock inte kunna dra nytta av dessa positiva effekter. Dessutom indikerar studiens resultat att lärarens användning av matteklippen spelar en stor roll när det kommer till hur matteklipp på nätet kan stödja elevers kunskapsutveckling. Nyckelord: Pedagogik, matematikdidaktik, IKT i undervisningen, Öppna lärresurser (OER), matteklipp på näte

Determination of Inter-Phase Line Tension in Langmuir Films

A Langmuir film is a molecularly thin film on the surface of a fluid; we study the evolution of a Langmuir film with two co-existing fluid phases driven by an inter-phase line tension and damped by the viscous drag of the underlying subfluid. Experimentally, we study an 8CB Langmuir film via digitally-imaged Brewster Angle Microscopy (BAM) in a four-roll mill setup which applies a transient strain and images the response. When a compact domain is stretched by the imposed strain, it first assumes a bola shape with two tear-drop shaped reservoirs connected by a thin tether which then slowly relaxes to a circular domain which minimizes the interfacial energy of the system. We process the digital images of the experiment to extract the domain shapes. We then use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions first verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%. We find line tensions in the range of 200-600 pN; we hypothesize that this variation is due to differences in the layer depths of the 8CB fluid phases.Comment: See (http://www.math.hmc.edu/~ajb/bola/) for related movie

Analysis of Three-Dimensional Scar Architecture and Conducting Channels by High-Resolution Contrast-Enhanced Cardiac Magnetic Resonance Imaging in Chagas Heart Disease

We aimed to describe the morphology of the border zone of viable myocardium surrounded by scarring in patients with Chagas heart disease and study their association with clinical events.Adult patients with Chagas heart disease (n=22; 55% females; 65.5 years, SD 10.1) were included. Patients underwent high-resolution contrast-enhanced cardiac magnetic resonance using myocardial delayed enhancement with postprocessing analysis to identify the core scar area and border zone channels number, mass, and length. The association between border zone channel parameters and the combined end-point (cardiovascular mortality or internal cardiac defibrillator implantation) was tested by multivariable Cox proportional hazard regression analyses. The significance level was set at 0.05. Data are presented as the mean (standard deviation [SD]) or median (interquartile range).A total of 44 border zone channels (1[1-3] per patient) were identified. The border zone channel mass per patient was 1.25 (0.48-4.39) g, and the extension in layers of the border zone channels per patient was 2.4 (1.0-4.25). Most border zone channels were identified in the midwall location. Six patients presented the studied end-point during a mean follow-up of 4.9 years (SD 1.6). Border zone channel extension in layers was associated with the studied end-point independent from left ventricular ejection fraction or fibrosis mass (HR=2.03; 95% CI 1.15-3.60).High-resolution contrast-enhanced cardiac magnetic resonance can identify border zone channels in patients with Chagas heart disease. Moreover, border zone channel extension was independently associated with clinical events

Anisotropic Condensation of Helium in Nanotube Bundles

Helium atoms are strongly attracted to the interstitial channels within a bundle of carbon nanotubes. The strong corrugation of the axial potential within a channel can produce a lattice gas system where the weak mutual attraction between atoms in neighboring channels of a bundle induces condensation into a remarkably anisotropic phase with very low binding energy. We estimate the binding energy and critical temperature for 4He in this novel quasi-one-dimensional condensed state. At low temperatures, the specific heat of the adsorbate phase (fewer than 2% of the total number of atoms) greatly exceeds that of the host material.Comment: 8 pages, 3 figures, submitted to PRL (corrected typo in abstract

Single- and multi-peak solitons in two-component models of metamaterials and photonic crystals

We report results of the study of solitons in a system of two nonlinear-Schrodinger (NLS) equations coupled by the XPM interaction, which models the co-propagation of two waves in metamaterials(MMs). The same model applies to photonic crystals (PCs), as well as to ordinary optical fibers, close to the zero-dispersion point. A peculiarity of the system is a small positive or negative value of the relative group-velocity dispersion (GVD) coefficient in one equation, assuming that the dispersion is anomalous in the other. In contrast to earlier studied systems of nonlinearly coupled NLS equations with equal GVD coefficients, which generate only simple single-peak solitons, the present model gives rise to families of solitons with complex shapes, which feature extended oscillatory tails and/or a double-peak structure at the center. Regions of existence are identified for single- and double-peak bimodal solitons, demonstrating a broad bistability in the system. Behind the existence border, they degenerate into single-component solutions. Direct simulations demonstrate stability of the solitons in the entire existence regions. Effects of the group-velocity mismatch (GVM) and optical loss are considered too. It is demonstrated that the solitons can be stabilized against the GVM by means of the respective "management" scheme. Under the action of the loss, complex shapes of the solitons degenerate into simple ones, but periodic compensation of the loss supports the complexity.Comment: Optics Communications, in press (Special Issue on Nonlinear Metamaterials

Differential column measurements using compact solar-tracking spectrometers

We demonstrate the use of compact solar-tracking Fourier transform spectrometers (Bruker EM27/SUN) for differential measurements of the column-averaged dry-air mole fractions of CH_4 and CO_2 within urban areas. Using Allan variance analysis, we show that the differential column measurement has a precision of 0.01 % for X_(CO_2) and X_(CH_4) with an optimum integration time of 10 min, corresponding to Allan deviations of 0.04 ppm and 0.2 ppb,respectively. The sensor system is very stable over time and after relocation across the continent. We report tests of the differential column measurement,and its sensitivity to emission sources, by measuring the downwind-minus-upwind column difference ΔX_(CH_4) across dairy farms in the Chino area, California, and using the data to verify emissions reported in the literature. Ratios of spatial column differences ΔX_(CH_4)∕ΔX_(CO_2) were observed across Pasadena within the Los Angeles basin, indicating values consistent with regional emission ratios from the literature. Our precise, rapid measurements allow us to determine significant short-term variations (5–10 min) of X_(CO_2) and X_(CH_4) and to show that they represent atmospheric phenomena. Overall, this study helps establish a range of new applicationsfor compact solar-viewing Fourier transform spectrometers. Byaccurately measuring the small differences in integrated column amounts acrosslocal and regional sources, we directly observe the mass loadingof the atmosphere due to the influence of emissions in theintervening locale. The inference of the source strength is muchmore direct than inversion modeling using only surface concentrationsand less subject to errors associated with small-scale transportphenomena