3,743 research outputs found
IMPACT: The Journal of the Center for Interdisciplinary Teaching and Learning. Volume 8, Issue 1, Winter 2019
IMPACT: The Journal of the Center for Interdisciplinary Teaching & Learning is a peer-reviewed, biannual online journal that publishes scholarly and creative non-fiction essays about the theory, practice and assessment of interdisciplinary education. Impact is produced by the Center for Interdisciplinary Teaching & Learning at the College of General Studies, Boston University (www.bu.edu/cgs/citl).In this issue of Impact you will find a humanities scholar deeply engaged with the arcing out of a new territory: the interdisciplinary study of the Grateful Dead. Impactâs own Christopher Coffmanâs review essay should be required reading for scholars of popular music, performance studies and history. His review also serves as an important reference for those who aspire to teach a course on the Grateful Dead, as well as for those who wish to write review essays. In this issue we also hear from those who are engaged in teaching people who are incarcerated. Importantly, Stephanie Cageâs essay looks to incarcerated people themselves to find out what they think about prison education. Peter Wakefield encourages us to see The Great Gatsby anew, in particular in the context of American racism and White supremacy. Wakefieldâs essay is important too because it had its genesis in Writing, the State, and the Rise of Neo-Nationalism: Historical Contexts and Contemporary Concerns, a conference sponsored by the Center for Interdisciplinary Teaching & Learning
Simulation of the effect of rainfall on farm-level cocoa yield using a delayed differential equation model
Cocoa (Theobroma cacao) is an economically important crop grown by approximately six million of smallholder farmers throughout the tropics and sub-tropics. However, farm level yields are often very low, and sustainable intensification is urgently required. Assessing the impact of on-farm interventions of farm productivity and profitability requires an understanding of the contribution of inter-annual climate variability to cocoa yields. A Delayed Differential Equation model (DDE) was used to simulate the effect of rainfall on cocoa yields. A DDE model is an ordinary differential equation model that incorporates time lags, and is therefore able to incorporate the delay in yield response to rainfall due interactions with the cocoa flowering and the pod development processes. The DDE was constructed and based on regional rainfall and farm-level cocoa yield data from 96 farms across the main cocoa growing regions in Ghana. Model outputs indicate that a good likeness of seasonality in crop production was achieved. The potential to conduct a detailed parameterisation and extend this model to include other parameters such as agrochemical inputs and farm management practices are discussed. By further developing this model into a useful tool to predict and understand variability in cocoa yield, the sustainable intensification of small holder cocoa farming is supported.</p
Congenital Nasal Pyriform Aperture Stenosis Repair: A Case Series and Discussion of Postoperative Care
Congenital nasal pyriform aperture stenosis (CNPAS) is a rare condition related to holoprosencephaly in which bony overgrowth of the medial nasal process of the maxilla narrows the pyriform aperture. CNPAS presents in neonates with signs of upper airway obstruction ranging from mild to severe respiratory distress and failure to thrive. Surgical intervention is indicated after failed conservative measures and generally includes temporary stent placement. We report a series of 3 cases of CNPAS treated surgically, examine postoperative care recommendations in the literature, and present a comprehensive postoperative care regimen with a novel method to maintain stent patency
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Radiometric Calibration of EAARLâB Bathymetric Lidar Data
The Experimental Advanced Airborne Research Lidar â B (EAARLâB), which was built and deployed by the U.S. Geological Survey (USGS) in 2014, is a novel topographicâbathymetric lidar system. While retaining a number of features that were pioneered in the original National Aeronautics and Space Administration (NASA) EAARL system (e.g., low energy, short pulse width, narrow receiver field of view, greenâonly laser wavelength), the EAARLâB added a splitâbeam, fourâchannel design to improve bathymetric data density and depth measurement range (up to 44 m in clear water). In 2014, the EAARLâB was used to acquire bathymetric data in the U.S. Virgin Islands (USVI), in support of the National Oceanic and Atmospheric Administration (NOAA) Center for Coastal Monitoring and Assessment (CCMA) Biogeography Branch. The enhanced capabilities of the EAARLâB system, combined with updated algorithms in the processing software, provided highâquality data covering over 600 km2 in the USVI, filling critical data gaps. However, the EAARLâB processing software and workflows were lacking a set of tools and procedures to exploit return waveforms (digitized samples of the backscattered signal) for generating seafloor reflectance mosaics and characterizing seafloor composition. This functionality is of significant interest to CCMA to support benthic habitat mapping and management of coral reef ecosystems. While seafloor reflectance mapping and waveform feature extraction tools do exist, in varying degrees and forms, for other bathymetric lidar systems, the extension of these capabilities to the EAARLâB is challenging, due to the systemâs unique design. The goal of this study was to address this need, through development and testing of a new set of processing procedures and algorithms for generating seafloor relative reflectance mosaics and gridded waveform features from EAARLâB data. The procedures were developed using data from two test sites: Barnegat Bay, New Jersey, and Buck Island, north of Saint Croix. After testing and refining the methods, a seafloor relative reflectance mosaic was generated for a large site south of Saint ï»żThomas. Additionally, raster grids of waveform shape features were produced for a smaller study site encompassing Flat Cays, south of Charlotte Amalie, Saint Thomas. The procedures have been demonstrated to enable generation of seamless seafloor data products, in which the effects of confounding variables, such as depth, incidence angle, and flight direction, have been virtually eliminated. Current research, led by project partners at NOAA CCMA and the University of New Hampshire, is focusing on using the results of this work to predict species richness, canopy cover, complexity, and coral health (including disease and bleaching) and other parameters for the USVI project sites.Keywords: intensity, Bathymetric lidar, radiometric calibratio
Interfacial band-edge energetics for solar fuels production
Photoelectrochemical (PEC) water splitting has received growing attention as a potential pathway to replace fossil fuels and produce a clean, renewable, and sustainable source of fuel. To achieve overall water splitting and the associated production of solar fuels, complex devices are needed to efficiently capture light from the sun, separate photogenerated charges, and catalyze reduction and oxidation reactions. To date, the highest performing solar fuels devices rely on multi-component systems, which introduce interfaces that can be associated with further performance loss due to thermodynamic and kinetic considerations. In this review, we identify several of the most important interfaces used in PEC water splitting, summarize methods to characterize them, and highlight approaches to mitigating associated loss mechanisms.The authors thank Dr Eric Miller for the inspiration to compile this
review, and the members of the U.S. Department of Energyâs
Photoelectrochemical Working Group and Task 35 (Renewable
Hydrogen) of the International E
nergy Agencyâs Hydrogen Imple-
menting Agreement for helpful comments, suggestions, and dis-
cussions, specifically Prof. Shane Ardo, Dr John Turner, Prof.
Dunwei Wang, and Prof. Shannon Boettcher. WAS greatly acknowl-
edges funding support from the FOM/NWO/Shell Program on CO
2
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neutral Fuels (Project â APPEL). IDS was supported by the Joint
Center for Artificial Photosynthesis, a DOE Energy Innovation Hub,
supported through the Office of Science of the U.S. Department of
Energy under Award Number DE-SC0004993. NCS acknowledges
start-up funds from Lehigh University. JB thanks financial support
from GeneralitatValenciana (ISIC/ 2012/008). A summary version of
this review paper (DOI: 10.2172/1209498), and associated summary
tables that will be updated as the field progresses, will be available
on the working group website (http://energy.gov/eere/fuelcells/
photoelectrochemical-working-group)
Visualizing electrostatic gating effects in two-dimensional heterostructures
The ability to directly observe electronic band structure in modern nanoscale
field-effect devices could transform understanding of their physics and
function. One could, for example, visualize local changes in the electrical and
chemical potentials as a gate voltage is applied. One could also study
intriguing physical phenomena such as electrically induced topological
transitions and many-body spectral reconstructions. Here we show that submicron
angle-resolved photoemission (micro-ARPES) applied to two-dimensional (2D) van
der Waals heterostructures affords this ability. In graphene devices, we
observe a shift of the chemical potential by 0.6 eV across the Dirac point as a
gate voltage is applied. In several 2D semiconductors we see the conduction
band edge appear as electrons accumulate, establishing its energy and momentum,
and observe significant band-gap renormalization at low densities. We also show
that micro-ARPES and optical spectroscopy can be applied to a single device,
allowing rigorous study of the relationship between gate-controlled electronic
and excitonic properties.Comment: Original manuscript with 9 pages with 4 figures in main text, 5 pages
with 4 figures in supplement. Substantially edited manuscript accepted at
Natur
Quantifying hurricane wind speed with undersea sound
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2006Hurricanes, powerful storms with wind speeds that can exceed 80 m/s, are one of the
most destructive natural disasters known to man. While current satellite technology
has made it possible to effectively detect and track hurricanes, expensive 'hurricanehunting'
aircraft are required to accurately classify their destructive power. Here
we show that passive undersea acoustic techniques may provide a promising tool for
accurately quantifying the destructive power of a hurricane and so may provide a safe
and inexpensive alternative to aircraft-based techniques.
It is well known that the crashing of wind-driven waves generates underwater
noise in the 10 Hz to 10 kHz range. Theoretical and empirical evidence are combined
to show that underwater acoustic sensing techniques may be valuable for measuring
the wind speed and determining the destructive power of a hurricane. This is done
by first developing a model for the acoustic intensity and mutual intensity in an
ocean waveguide due to a hurricane and then determining the relationship between
local wind speed and underwater acoustic intensity. Acoustic measurements of the
underwater noise generated by hurricane Gert are correlated with meteorological data
from reconnaissance aircraft and satellites to show that underwater noise intensity
between 10 and 50 Hz is approximately proportional to the cube of the local wind
speed. From this it is shown that it should be feasible to accurately measure the
local wind speed and quantify the destructive power of a hurricane if its eye wall
passes directly over a single underwater acoustic sensor. The potential advantages
and disadvantages of the proposed acoustic method are weighed against those of
currently employed techniques.
It has also long been known that hurricanes generate microseisms in the 0.1 to
0.6 Hz frequency range through the non-linear interaction of ocean surface waves.
Here we model microseisms generated by the spatially inhomogeneous waves of a
hurricane with the non-linear wave equation where a second-order acoustic field is
created by first-order ocean surface wave motion. We account for the propagation of
microseismic noise through range-dependent waveguide environments from the deep
ocean to a receiver on land. We compare estimates based on the ocean surface wave
field measured in hurricane Bonnie with seismic measurements from Florida.Finally, I am grateful to have been awarded the Office of Naval Research Graduate Traineeship Award in Ocean Acoustics. I also thank the MIT Sea Grant office for funding portions of this research
The Mass Function of Super Giant Molecular Complexes and Implications for Forming Young Massive Star Clusters in the Antennae (NGC 4038/39)
We have used previously published observations of the CO emission from the
Antennae (NGC 4038/39) to study the detailed properties of the super giant
molecular complexes with the goal of understanding the formation of young
massive star clusters. Over a mass range from 5E6 to 9E8 solar masses, the
molecular complexes follow a power-law mass function with a slope of -1.4 +/-
0.1, which is very similar to the slope seen at lower masses in molecular
clouds and cloud cores in the Galaxy. Compared to the spiral galaxy M51, which
has a similar surface density and total mass of molecular gas, the Antennae
contain clouds that are an order of magnitude more massive. Many of the
youngest star clusters lie in the gas-rich overlap region, where extinctions as
high as Av~100 imply that the clusters must lie in front of the gas. Combining
data on the young clusters, thermal and nonthermal radio sources, and the
molecular gas suggests that young massive clusters could have formed at a
constant rate in the Antennae over the last 160 Myr and that sufficient gas
exists to sustain this cluster formation rate well into the future. However,
this conclusion requires that a very high fraction of the massive clusters that
form initially in the Antennae do not survive as long as 100 Myr. Finally, we
compare our data with two models for massive star cluster formation and
conclude that the model where young massive star clusters form from dense cores
within the observed super giant molecular complexes is most consistent with our
current understanding of this merging system. (abbreviated)Comment: 40 pages, four figures; accepted for publication in Ap
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