Acoustic transmission through compound subwavelength slit arrays

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The angular dependence of the transmission of sound in air through four types of 2D slit-arrays formed of aluminium slats is explored, both experimentally and numerically. For a simple, subwavelength periodic slit-array, it is well known that Fabry-Perot-like wave-guide resonances, supported by the slit-cavities, hybridising with bound acoustic surface waves, result in ‘Enhanced Acoustic Transmission’ at frequencies determined by the length, width and separation of each slit-cavity. We demonstrate that altering the spacing or width of some of the slits to form a compound array (i.e. an array having a basis comprised of more than one slit) results in sharp dips in the transmission spectra, that may have a strong angular dependence. These features correspond to ‘phase resonances’, which have been studied extensively in the electromagnetic case. This geometry allows for additional near-field configurations compared to the simple array, whereby the field in adjacent cavities can be out-of-phase. Several types of compound slit-array are investigated; one such structure is optimised to minimise the effect of boundary-layer loss mechanisms present in each slit cavity, thereby achieving a deep, sharp transmission minimum in a broad maximumThe authors would like to thank the UK Ministry of Defence’s Defence Science and Technology Laboratorty (DSTL) for their financial support and permission to publis

The waveguiding of sound using lines of resonant holes

This is the final version. Available on open access from Nature Research via the DOI in this recordThe dispersion of an acoustic surface wave supported by a line of regularly spaced, open ended holes in an acrylic plate, is characterised by precise measurement of its localised acoustic fields. We illustrate the robust character of this surface wave and show its potential for control of sound by the acoustic waveguiding provided by a ring of regularly spaced holes.Defence Science and Technology Laboratory (DSTL

The challenges of constraining shelf sea tidal models using seabed sediment grain size as a proxy for tidal currents

This is the final version. Available from Elsevier via the DOI in this record.Past major changes in sea level have had a significant influence on global- and shelf sea tidal dynamics. Some of these changes are preserved in sedimentary records from the shelf seas, and so appropriate proxy data have the potential to constrain tidal model outputs over the recent geological past. Tidal models which simulate the evolution of tide-dependent parameters over geological timescales are fundamental to understanding the response of the tides to sea-level rise and climate change. This study explores a potential new sedimentary proxy for validating past shelf sea tidal dynamics, interrogating the relationship between tidally-modulated bed shear stress and seabed sediment grain size at discrete sediment core locations over the northwest European shelf seas. Radiocarbon-dated sediment grain size profiles were generated for four British Geological Survey UK shelf sediment vibrocores, spanning a range of physical environments. Changes in observed sediment grain size through time were compared with simulated changes in tidal-induced bed shear through time, using temporal and spatial outputs from the most recently developed palaeotidal model of the Northwest European shelf seas. Although a positive correlation between observed grain size and simulated bed shear stress was observed at three of the four sediment cores sites, no robust relationship could be quantified. The palaeotidal model output failed to resolve the details of the actual sediment dynamics, since only tidal-induced bed shear stresses were considered. Wave processes were neglected, and the model was not sensitive enough to constrain simulated past tidal conditions at point locations; rather it is suitable for examining general trends. There remains a need to develop new proxies for past shelf sea hydrodynamic conditions which can be used to constrain numerical model output of tidal currents at regional scales.Natural Environment Research Council (NERC

Classifying seabed sediment type using simulated tidal-induced bed shear stress

This is the author accepted manuscript. The final version is freely available from Elsevier via the DOI in this record.An ability to estimate the large-scale spatial variability of seabed sediment type in the absence of extensive observational data is valuable for many applications. In some physical (e.g., morphodynamic) models, knowledge of seabed sediment type is important for inputting spatially-varying bed roughness, and in biological studies, an ability to estimate the distribution of seabed sediment benefits habitat mapping (e.g., scallop dredging). Although shelf sea sediment motion is complex, driven by a combination of tidal currents, waves, and wind-driven currents, in many tidally energetic seas, such as the Irish Sea, long-term seabed sediment transport is dominated by tidal currents. We compare observations of seabed sediment grain size from 242 Irish Sea seabed samples with simulated tidal-induced bed shear stress from a three-dimensional tidal model (ROMS) to quantitatively define the relationship between observed grain size and simulated bed shear stress. With focus on the median grain size of well-sorted seabed sediment samples, we present predictive maps of the distribution of seabed sediment classes in the Irish Sea, ranging from mud to gravel. When compared with the distribution of well-sorted sediment classifications (mud, sand and gravel) from the British Geological Survey digital seabed sediment map of Irish Sea sediments (DigSBS250), this 'grain size tidal current proxy' (GSTCP) correctly estimates the observed seabed sediment classification in over 73% of the area.Funding was provided by the Natural Environment Research Council (NERC) through grant NE/I527853/1 (Ph.D. studentship to SLW). The authors are grateful for access to the seabed sediment sample data and would like to acknowledge colleagues collecting and preparing these data through the projects HABMAP, SWISS, IMAGIN, ADFISH, and various projects led by the JNCC, as well as Hilmar Hinz, Lee Murray and Gwladys Lambert for work undertaken on a project funded by the Isle of Man Government (Department of Environment, Food and Agriculture). The author acknowledges modelling support from Patrick Timko and Reza Hashemi. The digital seabed sediment map (DigSBS250) was kindly made available by the BGS. The model simulations were undertaken on High Performance Computing (HPC) Wales, a collaboration between Welsh universities, the Welsh Government and Fujitsu

Sensitivity of palaeotidal models of the northwest European shelf seas to glacial isostatic adjustment since the Last Glacial Maximum

This is the final version of the article. Available from Elsevier via the DOI in this record.The spatial and temporal distribution of relative sea-level change over the northwest European shelf seas has varied considerably since the Last Glacial Maximum, due to eustatic sea-level rise and a complex isostatic response to deglaciation of both near- and far-field ice sheets. Because of the complex pattern of relative sea level changes, the region is an ideal focus for modelling the impact of significant sea-level change on shelf sea tidal dynamics. Changes in tidal dynamics influence tidal range, the location of tidal mixing fronts, dissipation of tidal energy, shelf sea biogeochemistry and sediment transport pathways. Significant advancements in glacial isostatic adjustment (GIA) modelling of the region have been made in recent years, and earlier palaeotidal models of the northwest European shelf seas were developed using output from less well-constrained GIA models as input to generate palaeobathymetric grids. We use the most up-to-date and well-constrained GIA model for the region as palaeotopographic input for a new high resolution, three-dimensional tidal model (ROMS) of the northwest European shelf seas. With focus on model output for 1 ka time slices from the Last Glacial Maximum (taken as being 21 ka BP) to present day, we demonstrate that spatial and temporal changes in simulated tidal dynamics are very sensitive to relative sea-level distribution. The new high resolution palaeotidal model is considered a significant improvement on previous depth-averaged palaeotidal models, in particular where the outputs are to be used in sediment transport studies, where consideration of the near-bed stress is critical, and for constraining sea level index points.Funding was provided by the Natural Environment Research Council through grant NE/I527853/1 (Ph.D. studentship to SLW). The author acknowledges modelling support from Patrick Timko and Reza Hashemi. The model simulations were undertaken on High Performance Computing (HPC) Wales, a collaboration between Welsh universities, the Welsh Government and Fujitsu Laboratories of Europe. The authors also thank one anonymous reviewer and Dayton Dove for their thoughtful comments, and thorough and constructive reviews

Colorado Training Needs Assessment

The Colorado Department of Human Services (CO DHS) has contracted with the Cutler Institute for Health and Social Policy to assess the professional development needs of child welfare caseworkers, case aides, and supervisors. This needs assessment will help guide the development of the new Child Welfare Training Academy established by Governor Bill Ritter in May 2009. The Academy will provide child welfare professionals across the state with the training, skills and knowledge to better protect the state\u27s most vulnerable children from abuse and neglect

New Americans: Child Care Decision-Making of Refugee and Immigrant Parents of English Language Learners

The immigrant and refugee communities in the United States continue to increase. Denver, Colorado and Portland, Maine are two U.S. cities that reflect the changing demographics across the country. As these cities evolve and adjust to serve new populations, it becomes necessary to rethink deep-rooted culturally constructed patterns and traditions that do not take into account the beliefs and practices of these new cultures. One such tradition is child care. Because of the important link between preschool experiences and later school success, understanding refugee and immigrant families’ beliefs and decisions about child care is extremely important. From a policy perspective, understanding these beliefs can guide professional development training for child care providers serving these linguistically and culturally diverse families

Children at Risk in the Child Welfare System: Collaborations to Promote School Readiness - Final Report

This study examines the degree to which key players in the child welfare, early intervention/preschool special education (EI/Preschool SPED) and early care and education (ECE) systems (e.g. Head Start, preschool, child care centers, family child care homes) collaborate to meet the developmental needs of children ages 0 to 5 who are involved in the child welfare system. This research includes an analysis of data from the National Survey of Child and Adolescent Wellbeing (NSCAW) as well as a case study in Colorado involving interviews with key stakeholders and statewide surveys of caseworkers and foster parents

Is decoupling GDP growth from environmental impact possible?

© 2016 Ward et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The argument that human society can decouple economic growth-defined as growth in Gross Domestic Product (GDP)-from growth in environmental impacts is appealing. If such decoupling is possible, it means that GDP growth is a sustainable societal goal. Here we show that the decoupling concept can be interpreted using an easily understood model of economic growth and environmental impact. The simple model is compared to historical data and modelled projections to demonstrate that growth in GDP ultimately cannot be decoupled from growth in material and energy use. It is therefore misleading to develop growth-oriented policy around the expectation that decoupling is possible. We also note that GDP is increasingly seen as a poor proxy for societal wellbeing. GDP growth is therefore a questionable societal goal. Society can sustainably improve wellbeing, including the wellbeing of its natural assets, but only by discarding GDP growth as the goal in favor of more comprehensive measures of societal wellbeing