An official website of the United States government
When longshore transport systems encounter tidal inlets, complex mechanisms are involved in bypassing sand to downdrift barriers. Here, this process is examined at Plum Island Sound and Essex Inlets, Massachusetts, USA. One major finding from this study is that sand is transferred along the coast—especially at tidal inlets—by parcels, in discrete steps, and over decadal-scale periods. The southerly orientation of the main-ebb channel at Plum Island Sound, coupled with the landward migration of bars from the ebb delta to the central portion of the downdrift Castle Neck barrier island, have formed a beach protuberance. During the constructional phase, sand is sequestered at the protuberance and the spit-end of the barrier becomes sediment starved, leading to shoreline retreat and a broadening of the spit platform at the mouth to Essex Bay (downdrift side of Castle Neck). Storm-induced sand transport from erosion of the spit and across the spit platform is washed into Essex Bay, filling channels and enlarging flood deltas. This study illustrates the pathways and processes of sand transfer along the shoreline of a barrier-island/tidal-inlet system and provides an important example of the processes that future hydrodynamic and sediment-transport modeling should strive to replicate.
more »
« less
Enabling Self-passivation by Attaching Small Grains on Surfaces of Large Grains toward HighPerformance Perovskite LEDs
- Award ID(s):
- 1911659
- PAR ID:
- 10143607
- Date Published:
- Journal Name:
- iScience
- Volume:
- 19
- ISSN:
- 2589-0042
- Page Range / eLocation ID:
- 378– 387
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT Extremely elongated, conducting dust particles (also known as metallic ‘needles’ or ‘whiskers’) are seen in carbonaceous chondrites and in samples brought back from the Itokawa asteroid. Their formation in protostellar nebulae and subsequent injection into the interstellar medium have been demonstrated, both experimentally and theoretically. Metallic needles have been suggested to explain a wide variety of astrophysical phenomena, ranging from the mid-infrared interstellar extinction at $$\sim \,$$3–8$$\, {\rm \mu m}$$ to the thermalization of starlight to generate the cosmic microwave background. To validate (or invalidate) these suggestions, an accurate knowledge of the optics (e.g. the amplitude and the wavelength dependence of the absorption cross sections) of metallic needles is crucial. Here we calculate the absorption cross sections of iron needles of various aspect ratios over a wide wavelength range, by exploiting the discrete dipole approximation, the most powerful technique for rigorously calculating the optics of irregular or nonspherical grains. Our calculations support the earlier findings that the antenna theory and the Rayleigh approximation, which are often taken to approximate the optical properties of metallic needles, are indeed inapplicable.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/DOI:https://doi.org/10.1016/j.isci.2019.07.044
