Showing papers by "Michigan Technological University published in 2020"

Global lake responses to climate change

Abstract: Climate change is one of the most severe threats to global lake ecosystems. Lake surface conditions, such as ice cover, surface temperature, evaporation and water level, respond dramatically to this threat, as observed in recent decades. In this Review, we discuss physical lake variables and their responses to climate change. Decreases in winter ice cover and increases in lake surface temperature modify lake mixing regimes and accelerate lake evaporation. Where not balanced by increased mean precipitation or inflow, higher evaporation rates will favour a decrease in lake level and surface water extent. Together with increases in extreme-precipitation events, these lake responses will impact lake ecosystems, changing water quantity and quality, food provisioning, recreational opportunities and transportation. Future research opportunities, including enhanced observation of lake variables from space (particularly for small water bodies), improved in situ lake monitoring and the development of advanced modelling techniques to predict lake processes, will improve our global understanding of lake responses to a changing climate. Climate change affects lakes worldwide and is predicted to continue to alter lake ice cover, surface temperature, evaporation rates, water levels and mixing regimes. This Review discusses recent and expected lake responses to climate change and looks towards future research opportunities in lake monitoring and modelling.

Catechol-functionalized hydrogels: biomimetic design, adhesion mechanism, and biomedical applications.

Abstract: Hydrogels are a unique class of polymeric materials that possess an interconnected porous network across various length scales from nano- to macroscopic dimensions and exhibit remarkable structure-derived properties, including high surface area, an accommodating matrix, inherent flexibility, controllable mechanical strength, and excellent biocompatibility. Strong and robust adhesion between hydrogels and substrates is highly desirable for their integration into and subsequent performance in biomedical devices and systems. However, the adhesive behavior of hydrogels is severely weakened by the large amount of water that interacts with the adhesive groups reducing the interfacial interactions. The challenges of developing tough hydrogel-solid interfaces and robust bonding in wet conditions are analogous to the adhesion problems solved by marine organisms. Inspired by mussel adhesion, a variety of catechol-functionalized adhesive hydrogels have been developed, opening a door for the design of multi-functional platforms. This review is structured to give a comprehensive overview of adhesive hydrogels starting with the fundamental challenges of underwater adhesion, followed by synthetic approaches and fabrication techniques, as well as characterization methods, and finally their practical applications in tissue repair and regeneration, antifouling and antimicrobial applications, drug delivery, and cell encapsulation and delivery. Insights on these topics will provide rational guidelines for using nature's blueprints to develop hydrogel materials with advanced functionalities and uncompromised adhesive properties.

3D Graphene Materials: From Understanding to Design and Synthesis Control.

Abstract: Carbon materials, with their diverse allotropes, have played significant roles in our daily life and the development of material science. Following 0D C60 and 1D carbon nanotube, 2D graphene materi...

GOODD, a global dataset of more than 38,000 georeferenced dams

Abstract: By presenting the most comprehensive GlObal geOreferenced Database of Dams to date containing more than 38,000 dams as well as their associated catchments, we enable new and improved global analyses of the impact of dams on society and environment and the impact of environmental change (for example land use and climate change) on the catchments of dams. This paper presents the development of the global database through systematic digitisation of satellite imagery globally by a small team and highlights the various approaches to bias estimation and to validation of the data. The following datasets are provided (a) raw digitised coordinates for the location of dam walls (that may be useful for example in machine learning approaches to dam identification from imagery), (b) a global vector file of the watershed for each dam. Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.10538486

The Quijote Simulations

Abstract: The Quijote simulations are a set of 44,100 full N-body simulations spanning more than 7000 cosmological models in the hyperplane. At a single redshift, the simulations contain more than 8.5 trillion particles over a combined volume of 44,100 each simulation follows the evolution of 2563, 5123, or 10243 particles in a box of 1 h −1 Gpc length. Billions of dark matter halos and cosmic voids have been identified in the simulations, whose runs required more than 35 million core hours. The Quijote simulations have been designed for two main purposes: (1) to quantify the information content on cosmological observables and (2) to provide enough data to train machine-learning algorithms. In this paper, we describe the simulations and show a few of their applications. We also release the petabyte of data generated, comprising hundreds of thousands of simulation snapshots at multiple redshifts; halo and void catalogs; and millions of summary statistics, such as power spectra, bispectra, correlation functions, marked power spectra, and estimated probability density functions.

Contact angles: history of over 200 years of open questions

Abstract: The contact angle is one of the most sensitive experimental values describing a junction between three phases, being influenced by the composition and properties of contacting media as well as the ...

Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC

Abstract: We present the first catalog of gamma-ray sources emitting above 56 and 100 TeV with data from the High Altitude Water Cherenkov Observatory, a wide field-of-view observatory capable of detecting gamma rays up to a few hundred TeV. Nine sources are observed above 56 TeV, all of which are likely galactic in origin. Three sources continue emitting past 100 TeV, making this the highest-energy gamma-ray source catalog to date. We report the integral flux of each of these objects. We also report spectra for three highest-energy sources and discuss the possibility that they are PeVatrons.

Development of a neural interface for high-definition, long-term recording in rodents and nonhuman primates.

Abstract: Long-lasting, high-resolution neural interfaces that are ultrathin and flexible are essential for precise brain mapping and high-performance neuroprosthetic systems. Scaling to sample thousands of sites across large brain regions requires integrating powered electronics to multiplex many electrodes to a few external wires. However, existing multiplexed electrode arrays rely on encapsulation strategies that have limited implant lifetimes. Here, we developed a flexible, multiplexed electrode array, called "Neural Matrix," that provides stable in vivo neural recordings in rodents and nonhuman primates. Neural Matrix lasts over a year and samples a centimeter-scale brain region using over a thousand channels. The long-lasting encapsulation (projected to last at least 6 years), scalable device design, and iterative in vivo optimization described here are essential components to overcoming current hurdles facing next-generation neural technologies.

A review of open source ventilators for COVID-19 and future pandemics

Abstract: Coronavirus Disease 2019 (COVID-19) threatens to overwhelm our medical infrastructure at the regional level causing spikes in mortality rates because of shortages of critical equipment, like ventilators. Fortunately, with the recent development and widespread deployment of small-scale manufacturing technologies like RepRap-class 3-D printers and open source microcontrollers, mass distributed manufacturing of ventilators has the potential to overcome medical supply shortages. In this study, after providing a background on ventilators, the academic literature is reviewed to find the existing and already openly-published, vetted designs for ventilators systems. These articles are analyzed to determine if the designs are open source both in spirit (license) as well as practical details (e.g. possessing accessible design source files, bill of materials, assembly instructions, wiring diagrams, firmware and software as well as operation and calibration instructions). Next, the existing Internet and gray literature are reviewed for open source ventilator projects and designs. The results of this review found that the tested and peer-reviewed systems lacked complete documentation and the open systems that were documented were either at the very early stages of design (sometimes without even a prototype) and were essentially only basically tested (if at all). With the considerably larger motivation of an ongoing pandemic, it is assumed these projects will garner greater attention and resources to make significant progress to reach a functional and easily-replicated system. There is a large amount of future work needed to move open source ventilators up to the level considered scientific-grade equipment, and even further work needed to reach medical-grade hardware. Future work is needed to achieve the potential of this approach by developing policies, updating regulations, and securing funding mechanisms for the development and testing of open source ventilators for both the current COVID19 pandemic as well as for future pandemics and for everyday use in low-resource settings.

Pore-Edge Tailoring of Single-Atom Iron–Nitrogen Sites on Graphene for Enhanced CO2 Reduction

Abstract: Hosting atomically dispersed nitrogen-coordinated iron sites (Fe–N4) on graphene offers unique opportunities for driving electrochemical CO2 reduction reaction (CO2RR) to CO. However, the strong ad...

COVID-19: effective policymaking depends on trust in experts, politicians, and the public

Abstract: In a crisis, almost-instant choices about who to trust or distrust could make a difference between life and death. Trust is necessary for cooperation, coordination, social order, and to reduce the ...

Raman response and transport properties of tellurium atomic chains encapsulated in nanotubes

Abstract: Tellurium can form nanowires of helical atomic chains. With their unique one-dimensional van der Waals structure, these nanowires are expected to show physical and electronic properties that are remarkably different from those of bulk tellurium. Here, we show that few-chain and single-chain van der Waals tellurium nanowires can be isolated using carbon nanotube and boron nitride nanotube encapsulation. With this approach, the number of atomic chains can be controlled by the inner diameter of the nanotube. The Raman response of the structures suggests that the interaction between a single-atomic tellurium chain and a carbon nanotube is weak, and that the inter-chain interaction becomes stronger as the number of chains increases. Compared with bare tellurium nanowires on SiO2, nanowires encapsulated in boron nitride nanotubes exhibit a dramatically enhanced current-carrying capacity, with a current density of 1.5 × 108 A cm−2 that exceeds that of most semiconducting nanowires. We also use our tellurium nanowires encapsulated in boron nitride nanotubes to create field-effect transistors with a diameter of only 2 nm. By isolating one-dimensional tellurium nanowires in boron nitride nanotubes, the electronic properties of the atomic chains can be measured and the structures used to create field-effect transistors.

An International Laboratory Comparison of Dissolved Organic Matter Composition by High Resolution Mass Spectrometry: Are We Getting the Same Answer?

Abstract: High-resolution mass spectrometry (HRMS) has become a vital tool for dissolved organic matter (DOM) characterization. The upward trend in HRMS analysis of DOM presents challenges in data comparison ...

g-C3N4-based photoelectrodes for photoelectrochemical water splitting: a review

Abstract: Converting intermittent energies into green and storable chemical fuels (like hydrogen) is of great importance to address the global energy crisis and environmental issues. Photoelectrochemical (PEC) water splitting is a promising technology designed for this purpose, but its wide application relies significantly on the exploration of both economic and efficient electrode materials. g-C3N4 is a metal-free, low-cost and visible-light responsive semiconductor that shows great potential as a photoelectrode material for PEC water splitting. However, due to the inherent disadvantages of g-C3N4 and the difficulty in fabricating homogeneous and concrete g-C3N4 films, its PEC performance has encountered a bottleneck. For further attention on and breakthroughs in the development of g-C3N4-based photoelectrodes, this review commences with the basic principle of PEC water splitting. Then, recent progress in the strategies for improving the properties of g-C3N4 and the quality of g-C3N4 film electrodes is critically discussed, following the introduction of the basic structure of g-C3N4 as well as its advantages and challenges for PEC applications. Furthermore, current challenges in and future perspectives on obtaining g-C3N4-based electrodes for highly efficient and stable PEC water splitting are presented finally.

Atomically Dispersed Iron–Nitrogen Sites on Hierarchically Mesoporous Carbon Nanotube and Graphene Nanoribbon Networks for CO2 Reduction

Abstract: Atomically dispersed metal and nitrogen co-doped carbon (M-N/C) catalysts hold great promise for electrochemical CO2 conversion. However, there is a lack of cost-effective synthesis approaches to meet the goal of economic mass production of single-atom M-N/C with desirable carbon support architecture for efficient CO2 reduction. Herein, we report facile transformation of commercial carbon nanotube (CNT) into isolated Fe-N4 sites anchored on carbon nanotube and graphene nanoribbon (GNR) networks (Fe-N/CNT@GNR). The oxidization-induced partial unzipping of CNT results in the generation of GNR nanolayers attached to the remaining fibrous CNT frameworks, which reticulates a hierarchically mesoporous complex and thus enables a high electrochemical active surface area and smooth mass transport. The Fe residues originating from CNT growth seeds serve as Fe sources to form isolated Fe-N4 moieties located at the CNT and GNR basal plane and edges with high intrinsic capability of activating CO2 and suppressing hydrogen evolution. The Fe-N/CNT@GNR delivers a stable CO Faradaic efficiency of 96% with a partial current density of 22.6 mA cm-2 at a low overpotential of 650 mV, making it one of the most active M-N/C catalysts reported. This work presents an effective strategy to fabricate advanced atomistic catalysts and highlights the key roles of support architecture in single-atom electrocatalysis.

The energy crises revealed by COVID: Intersections of Indigeneity, inequity, and health

Abstract: The global COVID-19 pandemic is a health crisis, an economic crisis, and a justice crisis. It also brings to light multiple ongoing, underlying social crises. The COVID-19 crisis is actively revealing crises of energy sovereignty in at least four ways. First, there are many whose access to basic health services is compromised because of the lack of energy services necessary to provide these services. Second, some people are more vulnerable to COVID-19 because of exposure to environmental pollution associated with energy production. Third, energy services are vital to human wellbeing, yet access to energy services is largely organized as a consumer good. The loss of stable income precipitated by COVID-19 may therefore mean that many lose reliable access to essential energy services. Fourth, the COVID-19 crisis has created a window of opportunity for corporate interests to engage in aggressive pursuit of energy agendas that perpetuate carbon intensive and corporate controlled energy systems, which illuminates the ongoing procedural injustices of energy decision making. These four related crises demonstrate why energy sovereignty is essential for a just energy future. Energy sovereignty is defined as the right for communities, rather than corporate interests, to control access to and decision making regarding the sources, scales, and forms of ownership characterizing access to energy services. Energy sovereignty is a critical component in the design of a post-COVID-19 energy system that is capable of being resilient to future shocks without exacerbating injustices that are killing the most vulnerable among us.

Sex differences in self-report anxiety and sleep quality during COVID-19 stay-at-home orders.

Abstract: COVID-19 and home isolation has impacted quality of life, but the perceived impact on anxiety and sleep remains equivocal. The purpose of this study was to assess the impact of COVID-19 and stay-at-home orders on self-report anxiety and sleep quality, with a focus on sex differences. We hypothesized that the COVID-19 pandemic would be associated with increased anxiety and decreased sleep quality, with stronger associations in women. One hundred three participants (61 female, 38 ± 1 years) reported perceived changes in anxiety and sleep quality due to stay-at-home orders during the COVID-19 pandemic and were administered the Spielberger State-Trait Anxiety Inventory (STAI), Pittsburgh Sleep Quality Index (PSQI), and Insomnia Severity Index (ISI). Chi-square and T test analyses were utilized to assess sex differences in reported anxiety and sleep. Analysis of covariance was used to compare the associations between reported impact of COVID-19 and anxiety/sleep parameters. Women (80.3%) reported higher prevalence of increased general anxiety due to COVID-19 when compared to men (50%; p = 0.001) and elevated STAI state anxiety compared to men (43 ± 1 vs. 38 ± 1 a.u., p = 0.007). Despite these differences in anxiety, the perceived impact of COVID-19 on PSQI was not different between sexes. However, when stratified by perceived changes in anxiety due to COVID-19, participants with higher anxiety responses to COVID-19 had higher ISI compared to those with no perceived changes in anxiety (9 ± 1 vs. 5 ± 1 a.u., p = 0.003). Additionally, participants who reported reduced sleep quality due to COVID-19 reported higher state anxiety (45 ± 1 a.u.) compared to those that perceived no change (36 ± 2 a.u., p = 0.002) or increased (36 ± 2 a.u., p < 0.001) sleep quality. COVID-19 and state-ordered home isolation was associated with higher anxiety and reduced sleep quality, with a stronger association in women with respect to anxiety.

Big Data for a Big Country: The First Generation of Canadian Wetland Inventory Map at a Spatial Resolution of 10-m Using Sentinel-1 and Sentinel-2 Data on the Google Earth Engine Cloud Computing Platform

Abstract: Detailed information on the spatial distribution of wetlands is crucial for sustainable management and resource assessment. Furthermore, regularly updated wetland inventories are of particular impo...