Estimating total momentum at finite distances

We study the difficulties associated with the evaluation of the total Bondi momentum at finite distances around the central source of a general (asymptotically flat) spacetime. Since the total momentum is only rigorously defined at future null infinity, both finite distance and gauge effects must be taken into account for a correct computation of this quantity. Our discussion is applicable in general contexts but is particularly relevant in numerically constructed spacetimes for both extracting important physical information and assessing the accuracy of additional quantities.Comment: 10 pages, 1 figure. Typos corrected. Comments added and a new Appendix. To be published in PR

Rape Process Templates: A Hidden Cause of the Underreporting of Rape

Fewer than a third of rape victims report their rape to the police. This low reporting rate appears to exist not only in jurisdictions with police departments that intentionally discourage victims, but also, paradoxically, in areas with departments that believe they encourage victims to report and pursue allegations of rape. Relying on original qualitative research conducted with two local police departments (a city department and a university department) as a case study, this Note identifies a likely cause of the widespread underreporting­ rape process templates -and offers the foundation for a solution

Creating Conditions for Collaboration: A Case Study on Design-Based Professional Learning

Design thinking is a process for solving complex problems through creative actions. There are three primary ways design thinking is being used in education today: (a) as a teaching tool, (b) as a strategy for teachers to redesign their students’ learning experiences, and (c) as a tool for school leaders to design school change (Gallagher & Thordarson, 2018). Design thinking includes a strong emphasis on team-based learning regarding the problem and possible solutions (Lindberg et al., 2010). This case study describes one school’s approach to navigating complex challenges, inspiring school change, and developing conditions for meaningful collaboration using a design thinking-based approach to professional learning. The theoretical lenses of organizational learning and collective teacher efficacy were used to frame the study. Participants included school administrators, teachers, and instructional specialists from one high school who were a part of a design thinking-based professional learning program. Findings from the study indicate that school leaders held a desire to build capacity within the school and understand the importance of cultivating a positive school culture. Additionally, teachers found value in leading meaningful change, encountered resistance to change due to their roles as teachers, and were able to contextualize their work in the division-level initiative to be replicated their own school. All participants acknowledged the impact of COVID-19 on their school change process and that their momentum stalled as a result of the global pandemic. The results of this study can help guide educators as they implement inquiry-based activities that are team based, to create conditions for teachers and administrators to work collaboratively to solve complex problems, and to empower teacher leaders and administrators to establish efficacy and ownership in professional learning experiences

Matching factors for Delta S=1 four-quark operators in RI/SMOM schemes

The non-perturbative renormalization of four-quark operators plays a significant role in lattice studies of flavor physics. For this purpose, we define regularization-independent symmetric momentum-subtraction (RI/SMOM) schemes for Delta S=1 flavor-changing four-quark operators and provide one-loop matching factors to the MS-bar scheme in naive dimensional regularization. The mixing of two-quark operators is discussed in terms of two different classes of schemes. We provide a compact expression for the finite one-loop amplitudes which allows for a straightforward definition of further RI/SMOM schemes.Comment: 22 pages, 5 figure

Deuterium toward the WD0621-376 sight line: Results from the Far Ultraviolet Spectroscopic Explorer (FUSE) Mission

Far Ultraviolet Spectroscopic Explorer observations are presented for WD0621-376, a DA white dwarf star in the local interstellar medium (LISM) at a distance of about 78 pc. The data have a signal-to-noise ratio of about 20-40 per 20 km/s resolution element and cover the wavelength range 905-1187 \AA. LISM absorption is detected in the lines of D I, C II, C II*, C III, N I, N II, N III, O I, Ar I, and Fe II. This sight line is partially ionized, with an ionized nitrogen fraction of > 0.23. We determine the ratio $D/O = (3.9 \pm ^{1.3}_{1.0})\times 10^{-2}$ (2$\sigma$). Assuming a standard interstellar oxygen abundance, we derive ${\rm D/H} \approx 1. 3 \times 10^{-5}$. Using the value of N(H I) derived from EUVE data gives a similar D/H ratio. The D I/N I ratio is $(3.3 \pm ^{1.0}_{0.8})\times 10^{-1}$ (2$\sigma$).Comment: accepted for publication in the ApJ

Selection to minimise noise in living systems and its implications for the evolution of gene expression

Gene expression, like many biological processes, is subject to noise. This noise has been measured on a global scale, but its general importance to the fitness of an organism is unclear. Here, I show that noise in gene expression in yeast has evolved to prevent harmful stochastic variation in the levels of genes that reduce fitness when their expression levels change. Therefore, there has probably been widespread selection to minimise noise in gene expression. Selection to minimise noise, because it results in gene expression that is stable to stochastic variation in cellular components, may also constrain the ability of gene expression to respond to non-stochastic variation. I present evidence that this has indeed been the case in yeast. I therefore conclude that gene expression noise is an important biological trait, and one that probably limits the evolvability of complex living systems

A proposal for continuous loading of an optical dipole trap with magnetically guided ultra cold atoms

The capture of a moving atom by a non-dissipative trap, such as an optical dipole trap, requires the removal of the excessive kinetic energy of the atom. In this article we develop a mechanism to harvest ultra cold atoms from a guided atom beam into an optical dipole trap by removing their directed kinetic energy. We propose a continuous loading scheme where this is accomplished via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. We theoretically investigate the application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap. We discuss the realization of a suitable magnetic field configuration. Based on numerical simulations of the loading process we analyze the feasibility and efficiency of our loading scheme.Comment: 10 pages, 5 figure