Showing papers by "Michigan Technological University published in 2013"

Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions

Abstract: In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads. An extended period of weak lake circulation then led to abnormally long residence times that incubated the bloom, and warm and quiescent conditions after bloom onset allowed algae to remain near the top of the water column and prevented flushing of nutrients from the system. We further find that all of these factors are consistent with expected future conditions. If a scientifically guided management plan to mitigate these impacts is not implemented, we can therefore expect this bloom to be a harbinger of future blooms in Lake Erie.

Quantifying the consensus on anthropogenic global warming in the scientific literature

Abstract: We analyze the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991‐2011 matching the topics ‘global climate change’ or ‘global warming’. We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5%). Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus. For both abstract ratings and authors’ self-ratings, the percentage of endorsements among papers expressing a position on AGW marginally increased over time. Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.

Zinc Exhibits Ideal Physiological Corrosion Behavior for Bioabsorbable Stents

Abstract: Zinc is proposed as an exciting new biomaterial for use in bioabsorbable cardiac stents. Not only is zinc a physiologically relevant metal with behavior that promotes healthy vessels, but it combines the best behaviors of both current bioabsorbable stent materials: iron and magnesium. Shown here is a composite image of zinc degradation in a murine (rat) artery.

Biogeochemical processes and geotechnical applications: progress, opportunities and challenges

Abstract: Consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems. This is a new paradigm for many in geotechnical engineering. Realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification. This paper assesses the progress, opportunities, and challenges in this emerging field. Biomediated geochemical processes, which consist of a geochemical reaction regulated by subsurface microbiology, currently being explored include mineral precipitation, gas generation, biofilm formation and biopolymer generation. For each of these processes, subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals, organic matter, pore fluids, and gases that constitute soil. Geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance, sequestration of carbon, soil erosion control, groundwater flow control, and remediation of soil and groundwater impacted by metals and radionuclides. Challenges in biomediated ground modification include upscaling processes from the laboratory to the field, in situ monitoring of reactions, reaction products and properties, developing integrated biogeochemical and geotechnical models, management of treatment by-products, establishing the durability and longevity/reversibility of the process, and education of engineers and researchers.

Structural and Electrochemical Study of Al2O3 and TiO2 Coated Li1.2Ni0.13Mn0.54Co0.13O2 Cathode Material Using ALD

Abstract: Nanolayers of Al2O3 and TiO2 coatings were applied to lithium- and manganese-rich cathode powder Li1.2Ni0.13Mn0.54Co0.13O2 using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al2O3 surface film appeared to be uniform and conformal, while the TiO2 layers appeared as particulates across the material surface. In a Li-cell, the Al2O3 surface film was stable during repeated charge and discharge, and this improved the cell cycling stability, despite a high surface impedance. The TiO2 layer was found to be more reactive with Li and formed a LixTiO2 interface, which led to a slight increase in cell capacity. However, the repetitive insertion/extraction process for the Li+ ions caused erosion of the surface protective TiO2 film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li1.2Ni0.13Mn0.54Co0.13O2 and an anode of meso-carbon-micro-beads (MCMB), the cycling stability introduced by ALD was not enough to overcome the electrochemical instability of MCMB graphite. Therefore, protection of the cathode materials by ALD Al2O3 or TiO2 can address some of the capacity fading issues related to the Li-rich cathode at room temperature.

Laser speckle contrast imaging: theoretical and practical limitations

Abstract: When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide infor- mation about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale—the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle con- trast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimen- sional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its lim- itations and problems are investigated. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

Opportunities and challenges in carbon dioxide capture

Abstract: Various technologies for the capture of CO 2 from fossil fuel fired power plants are available. Each technology has its own advantages and disadvantages and are at different stages of development. This review provides a critical analysis of the major technologies for CO 2 capture from fossil fuel fired power plants so that the appropriate technology can be selected for a particular process. The different capture methods described in this review are: post-combustion, pre-combustion, oxy-combustion, and chemical looping combustion.

3D Honeycomb‐Like Structured Graphene and Its High Efficiency as a Counter‐Electrode Catalyst for Dye‐Sensitized Solar Cells

Abstract: Graphene, a two-dimensional carbon sheet, has attracted great interest due to its unique properties. To explore its practical applications, large-scale synthesis with controllable integration of individual graphene sheets is essential. To date, numerous approaches have been developed for graphene synthesis, including mechanical cleavage, epitaxial growth, and chemical vapor deposition. All of those techniques are used to prepare flat graphene sheets on a substrate. Chemical exfoliation of graphite has been applied to prepare graphene oxide solutions and graphene-based composite materials. Recently, tuning graphene shapes is attracting much attention. Cheng and co-workers synthesized graphene foam using porous Ni foam as a template for the CVD growth of graphene, followed by etching away the Ni skeleton. The graphene foam consists of an interconnected flexible network of graphene as the fast transport channel of charge carriers for high electrical conductivity. Ruoff et al. prepared porous graphene paper from microwave exfoliated graphene oxide by KOH activation. The porous graphene, which has an ultra-high surface area and a high electrical conductivity, was exploited for supercapacitor cells, leading to high values of gravimetric capacitance and energy density. Feng, M llen, and co-workers synthesized hierarchical macroand mesoporous graphene frameworks (GFs). The GFs exhibited excellent performance for electrochemical capacitive energy storage. Yu et al. and Qu et al. fabricated graphene tubes that could be selectively functionalized for desirable applications. Choi et al. synthesized macroporous graphene using polystyrene colloidal particles as sacrificial templates in graphene oxide suspension, and the pore sizes can be tuned by controlling template particle size. These important results represent a significant topic—tuning the properties of graphene sheets by controlling their shapes. However, it is still a challenge to synthesize three-dimensional graphene (3D) with a desirable shape. Herein, we develop a novel strategy for the synthesis of a new type of graphene sheet with a 3D honeycomb-like structure by a simple reaction between Li2O and CO. Furthermore, these graphene sheets exhibited excellent catalytic performance as a counter electrode for dye-sensitized solar cells (DSSCs) with an energy conversion efficiency as high as 7.8%, which is comparable to that of an expensive platinum electrode. Li2O is widely exploited as a promoter in catalysts to inhibit carbon formation. However, this general principle is challenged by this work, in which Li2O is used to react with CO to form graphene-structured carbon [Eq. (1)]

Consequences of cultural practices for entrepreneurial behaviors

Abstract: Although national culture is an important regulator of entrepreneurship, there is a dearth of studies that: (1) explore the effects of national cultural practices on entrepreneurial behaviors by individuals; (2) use appropriate multilevel research designs; (3) consider the effects of culture on different entrepreneurial behaviors, such as entry and post-entry growth aspirations. We combined Global Entrepreneurship Monitor (GEM) and Global Leadership and Organizational Behavior Effectiveness (GLOBE) data from 42 countries for 2005–2008 to address these gaps, using a multilevel design. We found societal institutional collectivism practices negatively associated with entrepreneurial entry, but positively associated with entrepreneurial growth aspirations. Uncertainty avoidance practices were negatively associated with entry but not with growth aspirations, and performance orientation practices were positively associated with entry. Our analysis highlights the differential effects of cultural practices on entrepreneurial entry and growth aspirations, and demonstrates the value of multilevel techniques in analyzing the effect of culture on entrepreneurship.

Uncertainty-Aware Household Appliance Scheduling Considering Dynamic Electricity Pricing in Smart Home

Abstract: High quality demand side management has become indispensable in the smart grid infrastructure for enhanced energy reduction and system control. In this paper, a new demand side management technique, namely, a new energy efficient scheduling algorithm, is proposed to arrange the household appliances for operation such that the monetary expense of a customer is minimized based on the time-varying pricing model. The proposed algorithm takes into account the uncertainties in household appliance operation time and intermittent renewable generation. Moreover, it considers the variable frequency drive and capacity-limited energy storage. Our technique first uses the linear programming to efficiently compute a deterministic scheduling solution without considering uncertainties. To handle the uncertainties in household appliance operation time and energy consumption, a stochastic scheduling technique, which involves an energy consumption adaptation variable , is used to model the stochastic energy consumption patterns for various household appliances. To handle the intermittent behavior of the energy generated from the renewable resources, the offline static operation schedule is adapted to the runtime dynamic scheduling considering variations in renewable energy. The simulation results demonstrate the effectiveness of our approach. Compared to a traditional scheduling scheme which models typical household appliance operations in the traditional home scenario, the proposed deterministic linear programming based scheduling scheme achieves up to 45% monetary expense reduction, and the proposed stochastic design scheme achieves up to 41% monetary expense reduction. Compared to a worst case design where an appliance is assumed to consume the maximum amount of energy, the proposed stochastic design which considers the stochastic energy consumption patterns achieves up to 24% monetary expense reduction without violating the target trip rate of 0.5%. Furthermore, the proposed energy consumption scheduling algorithm can always generate the scheduling solution within 10 seconds, which is fast enough for household appliance applications.

Ptr-miR397a is a negative regulator of laccase genes affecting lignin content in Populus trichocarpa.

Abstract: Laccases, as early as 1959, were proposed to catalyze the oxidative polymerization of monolignols. Genetic evidence in support of this hypothesis has been elusive due to functional redundancy of laccase genes. An Arabidopsis double mutant demonstrated the involvement of laccases in lignin biosynthesis. We previously identified a subset of laccase genes to be targets of a microRNA (miRNA) ptr-miR397a in Populus trichocarpa. To elucidate the roles of ptr-miR397a and its targets, we characterized the laccase gene family and identified 49 laccase gene models, of which 29 were predicted to be targets of ptr-miR397a. We overexpressed Ptr-MIR397a in transgenic P. trichocarpa. In each of all nine transgenic lines tested, 17 PtrLACs were down-regulated as analyzed by RNA-seq. Transgenic lines with severe reduction in the expression of these laccase genes resulted in an ∼40% decrease in the total laccase activity. Overexpression of Ptr-MIR397a in these transgenic lines also reduced lignin content, whereas levels of all monolignol biosynthetic gene transcripts remained unchanged. A hierarchical genetic regulatory network (GRN) built by a bottom-up graphic Gaussian model algorithm provides additional support for a role of ptr-miR397a as a negative regulator of laccases for lignin biosynthesis. Full transcriptome–based differential gene expression in the overexpressed transgenics and protein domain analyses implicate previously unidentified transcription factors and their targets in an extended hierarchical GRN including ptr-miR397a and laccases that coregulate lignin biosynthesis in wood formation. Ptr-miR397a, laccases, and other regulatory components of this network may provide additional strategies for genetic manipulation of lignin content.

Consequences of Cultural Practices for Entrepreneurial Behaviors

Abstract: Although national culture is an important regulator of entrepreneurship, there is a dearth of studies that (i) explore the effects of national cultural practices on entrepreneurial behaviors by individuals; (ii) use appropriate multi-level research designs; (iii) consider the effects of culture on different entrepreneurial behaviors such as entry and post-entry growth aspirations. We combined Global Entrepreneurship Monitor (GEM) and Global Leadership and Organizational Behavior Effectiveness (GLOBE) data from 42 countries for 2005-2008 to address these gaps using a multi-level design. We found societal institutional collectivism practices negatively associated with entrepreneurial entry but positively associated with entrepreneurial growth aspirations. Uncertainty avoidance practices were negatively associated with entry but not with growth aspirations, while performance orientation practices were positively associated with entry. Our analysis highlights the differential effects of cultural practices on entrepreneurial entry and growth aspirations and demonstrates the value of multi-level techniques in analyzing the effect of culture on entrepreneurship.

Rheological Properties and Chemical Bonding of Asphalt Modified with Nanosilica

Abstract: The objective of this study is to evaluate the rheological properties and chemical bonding of nano-modified asphalt binders blended with nanosilica In this study, the nanosilica was added to the control asphalt at contents of 4% and 6% based on the weight of asphalt binders Superpave binder and mixture tests were utilized in this study to estimate the characteristics of the nano-modifed asphalt binder and mixture The rotational viscosity (RV), dynamic shear rheometer (DSR), bending beam rhometer (BBR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), asphalt pavement analyzer (APA), dynamic modulus (DM) and flow number (FN) tests were used to analyze rheological properties and chemical bonding changes of the nano-modified asphalt binder and the performance of the nano-modified asphalt mixture In addition, the performance of nano-modified asphalt after rolling thin-film oven (RTFO) short-term and pressure-aging vessel (PAV) long-term aging was assessed as well

Morphology and mixing state of individual freshly emitted wildfire carbonaceous particles

Abstract: Biomass burning is a major source of carbonaceous particles, including tar balls and soot, that affect earth’s climate. Studying a wildfire plume, this work identifies two types of tar balls and classifies soot according to its mixing state with implications for the calculation of aerosol radiative forcing.

Mechanical properties of graphene nanoplatelet/epoxy composites

Abstract: Because of their high-specific stiffness, carbon-filled epoxy composites can be used in structural components in fixed-wing aircraft. Graphene nanoplatelets (GNPs) are short stacks of individual layers of graphite that are a newly developed, lower cost material that often increases the composite tensile modulus. In this work, researchers fabricated neat epoxy (EPON 862 with Curing Agent W) and 1–6 wt % GNP in epoxy composites. The cure cycle used for this aerospace epoxy resin was 2 h at 121°C followed by 2 h at 177°C. These materials were tested for tensile properties using typical macroscopic measurements. Nanoindentation was also used to determine modulus and creep compliance. These macroscopic results showed that the tensile modulus increased from 2.72 GPa for the neat epoxy to 3.36 GPa for 6 wt % (3.7 vol %) GNP in epoxy composite. The modulus results from nanoindentation followed this same trend. For loadings from 10 to 45 mN, the creep compliance for the neat epoxy and GNP/epoxy composites was similar. The GNP aspect ratio in the composite samples was confirmed to be similar to that of the as-received material by using the percolation threshold measured from electrical resistivity measurements. Using this GNP aspect ratio, the two-dimensional randomly oriented filler Halpin–Tsai model adjusted for platelet filler shape predicts the tensile modulus well for the GNP/epoxy composites. Per the authors' knowledge, mechanical properties and modeling for this GNP/epoxy system have never been reported in the open literature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

How culture moulds the effects of self-efficacy and fear of failure on entrepreneurship

Abstract: We use data from the Global Entrepreneurship Monitor and the Global Leadership and Organizational Behavior Effectiveness study for 42 countries to investigate how the effects of individual's self-efficacy and of fear of failure on entrepreneurial entry are contingent on national cultural practices. Using multi-level methodology, we observe that the positive effect of self-efficacy on entry is moderated by the cultural practices of institutional collectivism and performance orientation. Conversely, the negative effect of fear of failure on entry is moderated by the cultural practices of institutional collectivism and uncertainty avoidance. We discuss the implications for theory and methodological development in culture and entrepreneurship.

Preparing for climate change: Forestry and assisted migration

Abstract: Although plants have moved across the landscape in response to changing climate for millennia, projections of contemporary climate change suggest that forest tree species and populations will need to migrate faster than their natural ability. Therefore, climate change adaptation strategies, such as assisted migration, have gained attention since 2007. Effective implementation of assisted migration can only occur if target transfer guidelines are developed because our current seed transfer guidelines, established to guide the movement of plant materials, lack inherent spatial and temporal dynamics associated with climate change. This limitation restrains reforestation practitioners from making decisions about assisted migration. Lack of operating procedures, uncertainties about future climate conditions, risks associated with moving plants outside their current ranges, and existing policies have hampered formal actions in forest management and conservation. We review the current thinking on assisted migration of forest tree species and provide information that could facilitate implementation.

Distributed recycling of waste polymer into RepRap feedstock

Abstract: – A low‐cost, open source, self‐replicating rapid prototyper (RepRap) has been developed, which greatly expands the potential user base of rapid prototypers. The operating cost of the RepRap can be further reduced using waste polymers as feedstock. Centralized recycling of polymers is often uneconomic and energy intensive due to transportation embodied energy. The purpose of this paper is to provide a proof of concept for high‐value recycling of waste polymers at distributed creation sites., – Previous designs of waste plastic extruders (also known as RecycleBots) were evaluated using a weighted evaluation matrix. An updated design was completed and the description and analysis of the design is presented including component summary, testing procedures, a basic life cycle analysis and extrusion results. The filament was tested for consistency of density and diameter while quantifying electricity consumption., – Filament was successfully extruded at an average rate of 90 mm/min and used to print parts. The filament averaged 2.805 mm diameter with 87 per cent of samples between 2.540 mm and 3.081 mm. The average mass was 0.564 g/100 mm length. Energy use was 0.06 kWh/m., – The success of the RecycleBot further reduces RepRap operating costs, which enables distributed in‐home, value added, plastic recycling. This has implications for municipal waste management programs, as in‐home recycling could reduce cost and greenhouse gas emissions associated with waste collection and transportation, as well as the environmental impact of manufacturing custom plastic parts., – This paper reports on the first technical evaluation of a feedstock filament for the RepRap from waste plastic material made in a distributed recycling device.

Environmental Life Cycle Analysis of Distributed Three-Dimensional Printing and Conventional Manufacturing of Polymer Products

Abstract: With the recent development of the RepRap, an open-source self-replicating rapid prototyper, low-cost three-dimensional (3D) printing is now a technically viable form of distributed manufacturing o...

Volatile loss from melt inclusions in pyroclasts of differing sizes

Abstract: We have investigated the loss of H2O from olivine-hosted melt inclusions (MIs) by designing an experiment using tephra samples that cooled at different rates owing to their different sizes: ash, lapilli, and bomb samples that were deposited on the same day (10/17/74) of the sub-Plinian eruption of Volcan de Fuego in Guatemala. Ion microprobe, laser ablation-ICPMS, and electron probe analyses show that MIs from ash and lapilli record the highest H2O contents, up to 4.4 wt%. On the other hand, MIs from bombs indicate up to 30 % lower H2O contents (loss of ~1 wt% H2O) and 10 % post-entrapment crystallization of olivine. This evidence is consistent with the longer cooling time available for a bomb-sized clast, up to 10 min for a 3–4-cm radius bomb, assuming conductive cooling and the fastest H diffusivities measured in olivine (D~10−9 to 10−10 m2/s). On the other hand, several lines of evidence point to some water loss prior to eruption, during magma ascent and degassing in the conduit. Thus, results point to both slower post-eruptive cooling and slower magma ascent affecting MIs from bombs, leading to H2O loss over the timescale of minutes to hours. The important implication of this study is that a significant portion of the published data on H2O concentrations in olivine-hosted MIs may reflect unrecognized H2O loss via diffusion. This work highlights the importance of reporting clast and MI sizes in order to assess diffusive effects and the potential benefit of using water loss as a chronometer of magma ascent.

Open-Source 3D-Printable Optics Equipment

Abstract: Just as the power of the open-source design paradigm has driven down the cost of software to the point that it is accessible to most people, the rise of open-source hardware is poised to drive down the cost of doing experimental science to expand access to everyone. To assist in this aim, this paper introduces a library of open-source 3-D-printable optics components. This library operates as a flexible, low-cost public-domain tool set for developing both research and teaching optics hardware. First, the use of parametric open-source designs using an open-source computer aided design package is described to customize the optics hardware for any application. Second, details are provided on the use of open-source 3-D printers (additive layer manufacturing) to fabricate the primary mechanical components, which are then combined to construct complex optics-related devices. Third, the use of the open-source electronics prototyping platform are illustrated as control for optical experimental apparatuses. This study demonstrates an open-source optical library, which significantly reduces the costs associated with much optical equipment, while also enabling relatively easily adapted customizable designs. The cost reductions in general are over 97%, with some components representing only 1% of the current commercial investment for optical products of similar function. The results of this study make its clear that this method of scientific hardware development enables a much broader audience to participate in optical experimentation both as research and teaching platforms than previous proprietary methods.

Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour

Abstract: Nanodiamonds are small clusters of carbon that are of use in various nanotechnology applications such as spintronics, but are difficult to synthesize. Here Kumar et al. achieve the fabrication of nanodiamonds 2–5 nm in size at near-ambient conditions by a microplasma process.