Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

Atomic-Scale Observation of Lithiation Reaction Front in Nanoscale SnO2 Materials

Abstract: In the present work, taking advantage of aberration-corrected scanning transmission electron microscopy, we show that the dynamic lithiation process of anode materials can be revealed in an unprecedented resolution. Atomically resolved imaging of the lithiation process in SnO2 nanowires illustrated that the movement, reaction, and generation of b = [1[overline]1[overline]1] mixed dislocations leading the lithiated stripes effectively facilitated lithium-ion insertion into the crystalline interior. The geometric phase analysis and density functional theory simulations indicated that lithium ions initial preference to diffuse along the [001] direction in the {200} planes of SnO2 nanowires introduced the lattice expansion and such dislocation behaviors. At the later stages of lithiation, the Li-induced amorphization of rutile SnO2 and the formation of crystalline Sn and LixSn particles in the Li2O matrix were observed.

Brain temperature and limits on transcranial cooling in humans: quantitative modeling results

Abstract: Selective brain cooling (SBC) of varying strengths has been demonstrated in a number of mammals and appears to play a role in systemic thermoregulation. Although primates lack obvious specialization for SBC, the possibility of brain cooling in humans has been debated for many years. This paper reports on the use of mathematical modeling to explore whether surface cooling can control effectively the temperature of the human cerebrum. The brain was modeled as a hemisphere with a volume of 1.33 1 and overlying layers of cerebrospinal fluid, skull, and scalp. Each component was assigned appropriate dimensions, physical properties and physiological characteristics that were determined from the literature. The effects of blood flow and of thermal conduction were modeled using the steady-state form of the bio-heat equation. Input parameters included core (arterial) temperature: normal (37 degrees C) or hyperthermic (40 degrees C), air temperature: warm (30 degrees C) or hot (40 degrees C), and sweat evaporation rate: 0, 0.25, or 0.50 l x m(-2) x h(-1). The resulting skin temperatures of the model ranged from 31.8 degrees C to 40.2 degrees C, values which are consistent with data obtained from the literature. Cerebral temperatures were generally insensitive to surface conditions (air temperature and evaporation rate), which affected only the most superficial level of the cerebrum (< or =1.5 mm) The remaining parenchymal temperatures were 0.2-0.3 degrees C above arterial temperatures, regardless of surface conditions. This held true even for the worst-case conditions combining core hyperthermia in a hot environment with zero evaporative cooling. Modeling showed that the low surface-to-volume ratio, low tissue conductivity, and high rate of cerebral perfusion combine to minimize the potential impact of surface cooling, whether by transcranial venous flow or by conduction through intervening layers to the skin or mucosal surfaces. The dense capillary network in the brain assures that its temperature closely follows arterial temperature and is controlled through systemic thermoregulation independent of head surface temperature. A review of the literature reveals several independent lines of evidence which support these findings and indicate the absence of functionally significant transcranial venous flow in either direction. Given the fact that humans sometimes work under conditions which produce face and scalp temperatures that are above core temperature, a transcranial thermal link would not necessarily protect the brain, but might instead increase its vulnerability to environmentally induced thermal injury.

Green engineering: Environmentally conscious design of chemical processes and products

Abstract: The viewpoint advanced in this paper is that chemical engineers will require a new group of tools to address the challenges of green engineering and that these tools can fall into three categories: assessment, improvement, and integration.

The dawn of non-Hermitian optics

Abstract: Recent years have seen a tremendous progress in the theory and experimental implementations of non-Hermitian photonics, including all-lossy optical systems as well as parity-time symmetric systems consisting of both optical loss and gain. This progress has led to a host of new intriguing results in the physics of light–matter interactions with promising potential applications in optical sciences and engineering. In this comment, we present a brief perspective on the developments in this field and discuss possible future research directions that can benefit from the notion of non-Hermitian engineering. The concept of non-Hermitian parity-time reversal symmetry in optics has given rise to a vast amount of research aimed at exploring some of the exotic features displayed by photonics systems. The authors present a brief account of the state-of-the-art on non-Hermitian photonics and provide their perspective on the topic.

Response of Spawning Lake Sturgeons to Change in Hydroelectric Facility Operation

Abstract: Spawning of lake sturgeon Acipenser fulvescens was documented from 1987 to 1992 below the Prickett hydroelectric facility on the Sturgeon River, a tributary to Portage Lake, Michigan. Lake sturgeons were captured at the spawning site with dip nets during periods of reduced flow. A change in the spawning characteristics of the population was noted that corresponded to a change in the operation of the hydroelectric facility. In 1987 and 1988 the facility operated in a peaking mode, which resulted in large daily fluctuations in river flows. The years 1989 and 1990 were years of transition, and in 1991 and 1992 the facility released near run-of-the-river (ROR) flows. Under near-ROR flows, which were more natural, adult lake sturgeons spent 4–6 weeks less at the spawning sites, 74% more fish were observed, weights were greater due to a 68% increase in number of females, and fish had increased reproductive readiness. The change in flow regime was the result of a Federal Energy Regulatory Commission rel...