Fusing Binary Interface Defects in Topological Phases: The Vec⁡(Z/pZ)\operatorname{Vec}(\mathbb{Z}/p\mathbb{Z}) case

A binary interface defect is any interface between two (not necessarily invertible) domain walls. We compute all possible binary interface defects in Kitaev's $\mathbb{Z}/p\mathbb{Z}$ model and all possible fusions between them. Our methods can be applied to any Levin-Wen model. We also give physical interpretations for each of the defects in the $\mathbb{Z}/p\mathbb{Z}$ model. These physical interpretations provide a new graphical calculus which can be used to compute defect fusion.Comment: 27+10 pages, 2+5 tables, comments welcom

Testing eddy compensation and eddy saturation in the Southern Ocean

2013 Spring.Includes bibliographical references.The Southern Ocean (SO) is a unique and dynamic component of the climate system. Due in part to its cold temperatures and large surface area, the SO is an important region for the transfer of heat, momentum, and climatically relevant gases between the atmosphere and the interior ocean. The strong westerly winds above the SO help drive a powerful current (i.e. the Antarctic Circumpolar Current or ACC) that connects Earth's ocean basins in a global overturning circulation. In recent decades, these winds have strengthened and shifted poleward. Despite this change in surface forcing, no clear observational signal of the oceanic density structure's response has yet been detected. The eddy compensation hypothesis posits that changes in the direct wind-driven overturning circulation are balanced by changes in the eddy-induced meridional circulation, effectively rendering SO stratification insensitive to wind stress. The closely related (but not identical) eddy saturation hypothesis suggests that the ACC is also insensitive to increased wind stress, since additional energy ends up in the mesoscale eddy field instead of in the zonal mean circulation. In this work, we examine the viability of the eddy compensation and saturation hypotheses on interannual, decadal, and centennial timescales. Using a combination of theory and idealized numerical simulations, we show that it may take the Southern Ocean many decades to centuries to fully equilibrate with the world ocean following a change in wind stress. As such, it may be difficult to detect changes in isopycnal slope using the few decades of available observational data. We also explore the characteristics of eddy-driven interannual variability and examine how this variability may affect the decadal-scale adjustment of the global ocean. Our results suggest that departures from the eddy compensation regime may be important on decadal and centennial timescales, on which the interaction between regional Southern Ocean circulation and global ocean circulation is significant. As such, we suggest that Southern Ocean overturning circulation is likely to strengthen in response to recent and future climate change, with implications for the global carbon cycle and climate

Macroscopic and microscopic studies of electrical properties of very thin silicon dioxide subject to electrical stress

The electrical characteristics of various size tunnel switch diode devices, composed of Al/SiO2/n-Si/p+-Si layers, which operate with a range of parameters (such as current densities in excess of 104 A/cm2) that stress the oxide layer far beyond the levels used in typical thin oxide metal-oxide semiconductor research have been examined. It is found that the first time a large current and electric field are applied to the device, a "forming" process enhances transport through the oxide in the vicinity of the edges of the gate electrode, but the oxide still retains its integrity as a tunnel barrier. The device operation is relatively stable to stresses of greater than 107 C/cm2 areally averaged, time-integrated charge injection. Duplication and characterization of these modified oxide tunneling properties was attempted using scanning tunneling microscopy (STM) to stress and probe the oxide. Electrical stressing with the STM tip creates regions of reduced conductivity, possibly resulting from trapped charge in the oxide. Lateral variations in the conductivity of the unstressed oxide over regions roughly 20–50 nm across were also found

Freshwater flux from ice sheet melting and iceberg calving in the Southern Ocean

This dataset is a multiyear mean Southern Ocean freshwater flux field that uses recently compiled measurements of ice sheet melting, iceberg calving, iceberg tracking, and river runoff. It has a horizontal resolution of 1/6° and uses BEDMAP2 for identifying and placing individual ice sheets. The aim of this work is to improve the representation of Antarctic freshwater input in Southern Ocean models

Push-Pull PDV Analysis

Author Institution: Sandia National LaboratoriesSlides presented at the 2nd Annual Photonic Doppler Velocimetry (PDV) Workshop held at Lawrence Livermore National Laboratory, Livermore, California, August 16-17, 2007

Development of Modeling Approaches for Nuclear Thermal Propulsion Test Facilities

High efficiency of rocket propul-sion systems is essential for humanity to venture be-yond the moon. Nuclear Thermal Propulsion (NTP) is a promising alternative to conventional chemical rock-ets with relatively high thrust and twice the efficiency of the Space Shuttle Main Engine. NASA is in the pro-cess of developing a new NTP engine, and is evaluat-ing ground test facility concepts that allow for the thor-ough testing of NTP devices. NTP engine exhaust, hot gaseous hydrogen, is nominally expected to be free of radioactive byproducts from the nuclear reactor; how-ever, it has the potential to be contaminated due to off-nominal engine reactor performance. Several options are being investigated to mitigate this hazard potential with one option in particular that completely contains the engine exhaust during engine test operations. The exhaust products are subsequently disposed of between engine tests. For this concept (see Figure 1), oxygen is injected into the high-temperature hydrogen exhaust that reacts to produce steam, excess oxygen and any trace amounts of radioactive noble gases released by off-nominal NTP engine reactor performance. Water is injected to condense the potentially contaminated steam into water. This water and the gaseous oxygen (GO2) are subsequently passed to a containment area where the water and GO2 are separated into separate containment tanks

Prison as Seen by Convict Criminologists

Most criminologists tend to base their view of prison on ideological assumptions gathered from secondary sources, with at best limited entry to the prison world. They nearly always get it wrong, as they systematically exclude the perspectives and real life experiences of their human subjects. These academic researchers have contributed to poor public policy that promotes the violent repression of prisoners in the USA and other countries. In response, Convict Criminologists are ex‐convicts working as criminology and criminal justice professors, along with “non‐con” associates, that insist that as a means for societies to develop humane, effective, and cost efficient prisons, we must develop ways to incorporate the voice of prisoners in our theorizing about, policy recommendations for, and management of the prison

Domain walls in topological phases and the Brauer-Picard ring for Vec⁡(Z/pZ)\operatorname{Vec}(\mathbb{Z}/p\mathbb{Z})

We show how to calculate the relative tensor product of bimodule categories (not necessarily invertible) using ladder string diagrams. As an illustrative example, we compute the Brauer-Picard ring for the fusion category $\operatorname{Vec}(\mathbb{Z}/p\mathbb{Z})$. Moreover, we provide a physical interpretation of all indecomposable bimodule categories in terms of domain walls in the associated topological phase. We show how this interpretation can be used to compute the Brauer-Picard ring from a physical perspective.Comment: 16 pages, 1 figure, 3 tables, comments welcom

Promoter architecture dictates cell-to-cell variability in gene expression

Variability in gene expression among genetically identical cells has emerged as a central preoccupation in the study of gene regulation; however, a divide exists between the predictions of molecular models of prokaryotic transcriptional regulation and genome-wide experimental studies suggesting that this variability is indifferent to the underlying regulatory architecture. We constructed a set of promoters in Escherichia coli in which promoter strength, transcription factor binding strength, and transcription factor copy numbers are systematically varied, and used messenger RNA (mRNA) fluorescence in situ hybridization to observe how these changes affected variability in gene expression. Our parameter-free models predicted the observed variability; hence, the molecular details of transcription dictate variability in mRNA expression, and transcriptional noise is specifically tunable and thus represents an evolutionarily accessible phenotypic parameter