Pseudospin induced chirality with Staggered Optical Graphene

Pseudospin plays a very important role in understanding various interesting physical phenomena associated with 2D materials such as graphene. It has been proposed that pseudospin is directly related to angular momentum, and it was recently experimentally demonstrated that orbit angular momentum is an intrinsic property of pseudospin in a photonic honeycomb lattice. However, in photonics, the interaction between spin and pseudospin for light has never been investigated. In this Letter, we propose that, in an optical analogue of staggered graphene, i.e. a photonic honeycomb lattice waveguide with in-plane inversion symmetry breaking, the pseudospin mode can strongly couple to the spin of an optical beam incident along certain directions. The spin-pseudospin coupling, caused by the spin-orbit conversion in the scattering process, induces a strong optical chiral effect for the transmitted optical beam. Spin-pseudospin coupling of light opens door to the design of pseudospin-mediated spin or valley selective photonic devices

Projecting Changes in Extreme Precipitation in the Midwestern United States Using North American Regional Climate Change Assessment Program (NARCCAP) Regional Climate Models

Based on the physics of global circulation, many expect an enhanced greenhouse effect to lead to a more active hydrological cycle with more precipitation on average (Hennessy et al. 1997). This expected increase has been found in observations (Zhang et al. 2007) and has also been suggested by climate models, although these models are not consistent with respect to the spatial and temporal variability about this change. An increase in mean precipitation depth, assuming no change in the shape of the frequency distribution, would imply an increased frequency of heavy-precipitation events. However, some studies (Hennessy et al. 1997, Allen and Soden, 2008) also suggest the increase in these extreme events could be disproportionate to the change in the mean, with a greater fraction of the total precipitation being delivered by such heavy precipitation events. Such a shift towards heavy events is a common conclusion of climate models (Cubasch et al. 2001, Meehl et al. 2007) as well as analyses of observed rainfall data at the continental scale (Easterling 2000, Kunkel 2003, Groisman 2005, Min et al. 2011). However, there is great spatial variation of this average pattern. This study aims to establish likely future projections for how extreme precipitation frequency and magnitude could change in the Midwestern region of the United States, and investigate the spatial variation of such changes within the area. Present global climate models (GCMs) typically produce results at the spatial resolution of 150-300 km. This level of spatial resolution of GCMs is insufficient for establishing localized future climate projections and examining their spatial variations at the scale of a state. For increased spatial resolution, we used a set of Regional Climate Models (RCMs) run by National Center for Atmospheric Research (NCAR) under the North American Regional Climate Change Assessment Program (NARCCAP). RCMs involve nesting a higher resolution climate models within a coarser resolution GCM. The GCM output is used to define boundary conditions around a limited domain, within which RCM further models the physical dynamics of the climate system. These RCMs are designed to produce high resolution climate change simulations in order to investigate uncertainties in regional scale projections of future climate and generate climate change scenarios for use in regional and local impacts research (Mearns et al, 2009). This study aims to achieve two main objectives. First, we evaluate the performance of NARCCAP models in terms of whether they capture the frequency distribution of daily precipitation data. This evaluation is based on a comparison of retrospective model runs with observed station-based daily precipitation data. Second, based on the evaluation, we correct the bias in mean precipitation and frequency distribution of precipitation output from RCMs. After the model biases have been corrected, we then project future changes of mean and extreme precipitation patterns in the Midwest Region

DOC 2020-02 Proposal to Rename the Department of Geology to the Department of Geology and Environmental Geosciences

Legislative Authority RATIONALE: The Department of Geology formally propose to change its name to the Department of Geology and Environmental Geosciences. Geology is a scientific discipline that deals with the Earth\u27s physical structure and chemical composition, its history, and processes that shape the planet. Traditionally, geologists study the rocks, map the mountains and discover fossils to explain the landscape, discover the workings of the continents and the deep Earth, and put together the history of the Earth’s physical environment and biological evolution. In practical applications, geologists also find groundwater resources, energy resources, and mineral deposits of great economic values. Recent decades have seen increasing awareness that many challenges we face as a society, particularly significant environmental problems, require collaborative effort that transcends traditional disciplinary boundaries. As a result, geology departments across the country at both small and large universities have expanded their scope and embrace a wider range of fields of inquiry related to the planet Earth, such as climatology, hydrology, glaciology and oceanography. To capture the changing nature of the field, many departments have also changed their names from the traditional “geology” to “Earth science” or “geoscience” or some combination of environment and geology to show the breadth of their strength. Some recent examples near us include Miami University and Indiana University. Today, an Earth science or geoscience degree encompasses a wider set of subjects and a more global perspective than a traditional geology degree a few decades back. To that end, it studies all of Earth\u27s dynamic processes in the geosphere, atmosphere, hydrosphere and cryosphere in order to better prepare students to tackle the 21st century society’s pressing geological and environmental challenges. This change is also happening in the Geology Department at UD. The most direct and obvious evidence of such changes lies in the faculty hired in the department. Below is a list of all full-time faculty members with their area of expertise in the order of their time of hire: Michael Sandy (1987): paleontology, sedimentology and stratigraphy Don Pair (1991): glacial geology, geomorphology Andrea Koziol (1993): mineralogy Allen McGrew (1995): structural geology, tectonics Daniel Goldman (1997): paleobiology, quantitative biostratigraphy, sedimentology and stratigraphy Shuang-Ye Wu (2004): climatology, climate change, GIS Umesh Haritashya (2008): glaciology, climate change, hydrology, remote sensing Zelalem Bedaso (2013): environmental geochemistry, paleoclimate and paleo-environment, isotope hydrology. Andrew Rettig (2019): geography, environmental sensor network It can be seen from this list that the Geology department has followed the trend of incorporating environmental aspects of geosciences that go beyond those traditionally associated with geology. Faculty hired prior to 2000 are mostly traditional geologists, compared to the environmental geoscience and global change focused faculty hiring post-2000. This shift is also reflected in faculty research, course offerings and student mentoring. Furthermore, here at UD, we have a long history of graduating students who have become leaders in the various geological and environmental industries. In recent years most of our students have gone on to join the industry or graduate schools dealing with the environmental issues. Their feedback suggests that it would be easier for them to present their credentials if they can say that they have graduated from an Environmental Geosciences department as compared to the traditional geology department. Therefore, we believe that this department name change is not only appropriate but necessary to truly capture the mission of the department and the associated breadth of the research and teaching interests, as well as to help students navigate the changing job market. The proposed Department of Geology and Environmental Geosciences is a common name adopted in US universities. The exact same name is used in the North Illinois University, Bucknell University, College of Charleston, and a similar name is used in the Miami University at Oxford, Ohio (Department of Geology and Environmental Earth Sciences). The department will offer the following programs: Bachelor of Science (B. S.) in Geology (GEO) Bachelor of Science (B. S.) in Environmental Geosciences (EVG) Minor in Geosciences (GEO) No major changes in the curriculum are required for this name change, as the former B. S. program in environmental geology already encompasses the broad range of classes that can be characterized as environmental geosciences. Minor revisions are being proposed to better align the curriculum to the degree programs. We believe this name change will also help attract students with interests in environmental sciences, and potentially increase our majors’ enrollment. Impacts on other departments and programs at UD will be minimal and potentially beneficial by re-focusing the core mission and strengths of the department to better align with and closely support allied programs of environmental biology (EVB) and the newly developed Sustainability program (SEE). Science-minded SEE majors often consider double-majoring in either EVG or EVB. Therefore, the change in department name could potentially help the SEE program and our programs at the same time to attract more students by effectively coordinating our offerings. Since most EVB students enter that program with Biology in mind, this change should have little impact on that department. From our contact with potential students, we found that there exist a body of students who are environmentally inclined but do not wish to pursue biology. They are looking for a non-biology tract of the environmental offering. With the name change, we hope to attract the attention of and provide an opportunity for this group of students who may otherwise go to another university. Overall, we believe the impact on EVB, SEE, or any other department will be minimal and in the long run even beneficial by realigning the geoscience mission and curricula in ways likely to better support the needs of these majors. We emphasize that this is not a “zero-sum” game: by broadening and strengthening the environmental focus at the University we expect all environmental programs at the University to benefit by better positioning the University of Dayton to attract environmentally-oriented students. This proposal is supported by the science departments and the SEE program

Impact of Icebergs on Net Primary Productivity in the Southern Ocean

Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide a comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small-scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity at the scale of the SO, using remote sensing data of iceberg occurrences and ocean net primary productivity (NPP) covering the period 2002–2014. The impacts of both large and small icebergs are examined in four major ecological zones of the SO: the continental shelf zone (CSZ), the seasonal ice zone (SIZ), the permanent open ocean zone (POOZ), and the polar front zone (PFZ). We found that the presence of icebergs is associated with elevated levels of NPP, but the differences vary in different zones. Grid cells with small icebergs on average have higher NPP than other cells in most iron-deficient zones: 21 % higher for the SIZ, 16 % for the POOZ, and 12 % for the PFZ. The difference is relatively small in the CSZ where iron is supplied from meltwater and sediment input from the continent. In addition, NPP of grid cells adjacent to large icebergs on average is 10 % higher than that of control cells in the vicinity. The difference is larger at higher latitudes, where most large icebergs are concentrated. From 1992 to 2014, there is a significant increasing trend for both small and large icebergs. The increase was most rapid in the early 2000s and has leveled off since then. As the climate continues to warm, the Antarctic Ice Sheet is expected to experience increased mass loss as a whole, which could lead to more icebergs in the region. Based on our study, this could result in a higher level of NPP in the SO as a whole, providing a possible negative feedback for global warming in near future

Paleogeographic, Paleoceanographic, and Tectonic Controls on Early Late Ordovician Graptolite Diversity Patterns

The Katian Age (early Late Ordovician) was a time of significant decline in marine biodiversity, but whether this decline was a real phenomenon or an artifact of the relatively few studies devoted to this interval requires further research. We examined the pattern of graptolite faunal changes across the boundary between the Climacograptus bicornis and Diplacanthograptus caudatus graptolite zones in North America and on several other continents. A sharp decline in species diversity occurs in the Appalachian Basin. Scores for normalized diversity dropped from 20 in the C. bicornis Zone to 7 in the D. caudatus Zone. Only 11% of the species present in the C. bicornis Zone carry over into the D. caudatus Zone. A similar pattern occurs in central Oklahoma. Regions at higher paleolatitude, such as Wales and Baltoscandia, exhibit low graptolite diversity in lower Katian strata, and then diversity declines further in higher strata. In other regions at low paleolatitude, such as Australasia and Scotland, however, diversity is fairly constant across this interval (although the percentage of carryover taxa remains low). We conclude that seawater temperature change or disruption of the oceanic density structure, which might accompany temperature change, provides explanations for the similarity between Laurentian and higher paleolatitude diversity patterns. Flooding of the Laurentian craton through the Sebree Trough by cool, subpolar Iapetus seawater may have adversely affected graptolite diversity there. Regions at high paleolatitudes likely underwent cooling associated with Katian climate deterioration. Thus seawater cooling, albeit driven by different mechanisms, may have produced similar diversity patterns at different paleolatitudes