Optical diode based on the chirality of guided photons

Photons are nonchiral particles: their handedness can be both left and right. However, when light is transversely confined, it can locally exhibit a transverse spin whose orientation is fixed by the propagation direction of the photons. Confined photons thus have chiral character. Here, we employ this to demonstrate nonreciprocal transmission of light at the single-photon level through a silica nanofibre in two experimental schemes. We either use an ensemble of spin-polarised atoms that is weakly coupled to the nanofibre-guided mode or a single spin-polarised atom strongly coupled to the nanofibre via a whispering-gallery-mode resonator. We simultaneously achieve high optical isolation and high forward transmission. Both are controlled by the internal atomic state. The resulting optical diode is the first example of a new class of nonreciprocal nanophotonic devices which exploit the chirality of confined photons and which are, in principle, suitable for quantum information processing and future quantum optical networks

Forested wetlands for water resource management in southern Illinois

A 30 ha cypress - tupelo (Taxodium distichum - Nyssa aquatics), floodplain swamp in Southern Illinois was studied for its hydrologic, biogeochemical and ecological characteristics. The hydrology, water chemistry, sediment dynamics and ecosystem productivity were described for the swamp and interactions with the adjacent Cache River were emphasized. A representative flood in the spring spilled water and sediments from the river to the swamp, temporarily reversing the normal flow of water from the swamp to the river. The annual hydrology budget for the swamp showed inflows of 7'4.4 cm throughfall, 63.9 cm runoff, and 21.9 cm groundwater; the outflows were 7'2.8 cm evapotranspiration, 54.9 cm surface outflow, and 21.0 cm groundwater, the latter two draining to the river. Loading rates for several chemical parameters were calculated from the swamp to the river and water chemistry of the swamp and river was contrasted. Primary productivity measurements showed high rates when the floating duckweed was included; cypress productivity was shown historically to be related to amount of flooding. A phosphorus budget was determined for the swamp and this indicated that the flooding river contributed over 10 times the phosphorus to the swamp as was discharged the rest of the year.U.S. Department of the InteriorU.S. Geological SurveyOpe

Estimation and comparison of gross primary productivity patterns in created riparian wetlands

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Wetlands and Coal Surface Mining: A Management Handbook

As the third phase of a three-year project, this report outlines management options for protecting wetlands during the surface mining of coal, particularly for the portion of the Eastern Interior Coal Region that is found in Kentucky, Indiana, and Illinois. It is presented in manual form for use by coal mine operators, regulatory agencies and research institutions. The previous phases of the project produced an atlas of the most heavily-mined areas of the western Kentucky coal field, which classified and identified wetlands in these areas, and discussed some specific impacts of mining on these wetlands. The need to present information that will lead to action by coal operations and regulatory agencies to protect wetland areas, is the incentive for this report. The main issues addressed in this the manual include: basic information for identifying wetlands; wetland values, and methods used for values assessment; how coal surface mining can affect wetlands; a method for addressing wetland protection needs and some prevention and mitigation actions; reclamation alternatives, including wetland restoration and the creation of wetlands as alternative ecosystems on mined areas; and general legal and regulatory information concerning wetland protection and surface mining of coal. Information was gathered through a search of current literature and by contact with state and federal agencies, some coal mining operations, and other concerned organizations. A detailed listing of places to go for more information is included as an appendix

Dispersive Optical Interface Based on Nanofiber-Trapped Atoms

We dispersively interface an ensemble of one thousand atoms trapped in the evanescent field surrounding a tapered optical nanofiber. This method relies on the azimuthally-asymmetric coupling of the ensemble with the evanescent field of an off-resonant probe beam, transmitted through the nanofiber. The resulting birefringence and dispersion are significant; we observe a phase shift per atom of $\sim$\,1\,mrad at a detuning of six times the natural linewidth, corresponding to an effective resonant optical density per atom of 0.027. Moreover, we utilize this strong dispersion to non-destructively determine the number of atoms.Comment: 4 pages, 4 figure

Potential for long-term transfer of dissolved organic carbon from riparian zones to streams in boreal catchments

Boreal regions store most of the global terrestrial carbon, which can be transferred as dissolved organic carbon (DOC) to inland waters with implications for both aquatic ecology and carbon budgets. Headwater riparian zones (RZ) are important sources of DOC, and often just a narrow ‘dominant source layer' (DSL) within the riparian profile is responsible for most of the DOC export. Two important questions arise: how long boreal RZ could sustain lateral DOC fluxes as the sole source of exported carbon and how its hydromorphological variability influences this role. We estimate theoretical turnover times by comparing carbon pools and lateral exports in the DSL of 13 riparian profiles distributed over a 69km2 catchment in northern Sweden. The thickness of the DSL was 36±18 (average ± SD) cm. Thus, only about one-third of the 1-m-deep riparian profile contributed 90% of the lateral DOC flux. The 13 RZ exported 8.7±6.5g C m-2year-1, covering the whole range of boreal stream DOC exports. The variation could be explained by local hydromorphological characteristics including RZ width (R2=0.90). The estimated theoretical turnover times were hundreds to a few thousands of years, that is there is a potential long-lasting supply of DOC. Estimates of net ecosystem production in the RZ suggest that lateral fluxes, including both organic and inorganic C, could be maintained without drawing down the riparian pools. This was supported by measurements of stream DO14C that indicated modern carbon as the predominant fraction exported, including streams disturbed by ditching. The transfer of DOC into boreal inland waters from new and old carbon sources has a major influence on surface water quality and global carbon balances. This study highlights the importance of local variations in RZ hydromorphology and DSL extent for future DOC fluxes under a changing climate

Classification and Management of Wetlands in the Western Kentucky Coal Field

This is the first research report of a three-year project on wetland identification and management criteria in the western Kentucky coal field. The region is approximately 12,000 square kilometers and, due to its slight relief, contains many wetlands, some contiguous with surface coal mining operations. The overall objectives of the research project are 1) to identify, classify, and map wetlands in the western Kentucky coal field; 2) to evaluate the major biotic and abiotic factors that affect those wetlands; and 3) to develop strategies for the proper management of those wetlands. The first report of this three-year project has involved the following tasks related to wetlands in the coal fields of western Kentucky: establishment of three intensive study sites in major wetlands for identification and assessment of management impacts, sampling tripe in May, July, and September to the intensive study sites, to measure water quality and ecological structure, development of a classification specifically for wetlands in western Kentucky and an application of the classification to the three intensive study sites, and development of conceptual models of the region, watersheds, and specific ecosystems, and preliminary simulations of a wetland model. Our specific sites in western Kentucky are Cypress Creek Wetlands in Muhlenberg County, which are affected by mine drainage and channelization; Clear Creek Swamp in Hopkins County, which is affected by mine drainage and higher water levels; and Henderson Sloughs in Henderson County, which are affected by oil wells and clearing for agriculture. Preliminary analysis of field surveys demonstrates that several activities, particularly coal mining and oil \u27extraction, may affect the health of wetlands in western Kentucky. Drainage, logging, channelization, and impoundments have also caused significant alterations