Choking Off Research Articles

Model-Informed Si Electrode Design Considering Dynamic Pore-Closure and Stack Pressure Effects

Silicon is novel Li-ion battery anode chemistry with exceptional theoretical energy densities. However, this alloying material has significant challenges with non-passivating solid-electrolyte interface (SEI) formation and significant chemo-mechanics issues. These issues have been studied extensively at the particle-level. However, extensive SEI formation and dynamic particle chemo-mechanics need to be accounted for when designing the overall electrode microstructure. For example, Si particle expansion can result in electrolyte pore-closure. During charging (Si lithiation), Si particles near the separator lithiate faster than Si near the current-collector. Thus, Si particles near the separator begin to expand faster and close-off electrolyte access to particles near the current collector. This heterogeneous through-plane lithiation then results in low overall electrode utilization, especially at high rates (i.e.,>1 C). The “choking off” effect is a result of a strong feedback between heterogeneous lithiation, Si expansion, and electrolyte pore closure.To aid in Si electrode design and account for dynamic particle expansion/contraction, the standard pseudo-2D battery model is reformulated to account for finite-strain chemo-mechanics. This model explores the trade-offs between initial electrode porosity, electrode thickness, rate-capability, and external pressure. Additionally, the model implements simplified SEI growth dynamics to explore how SEI growth effects should be accounted for in electrode design.The Figure illustrates polarization responses for a 1C charge for a Si/NMC532 cell. The different colors indicate different initial anode porosities. As shown in Figure a, the low initial porosity cases results in significant polarization, but additional gains after 50% initial porosity are significantly diminished. These results are shown for an external pressure of 15 psi. Figure b illustrates the cell thickness as a function of time. As illustrated, the lower porosity case starts at a shorter initial thickness. For all cases, the cell thickness increases as Si lithiates/expands. Figure c illustrates the anode porosity at the cut-off voltage as a function of anode thickness. As shown, the lower initial porosity case has significant pore-closure on the right-side at the separator interface. The higher initial porosity cases have increased anode lengths because the Si utilization is improved due to the reduced pore-closer effects. The graphic illustrates the main features of the reformulated pseudo-2D battery model. Figure 1

Tox and Detox

Tox and Detox

Reviews of Science for Science Librarians: The 40th Anniversary of Dr. Colin Sullivan’s Invention of Continuous Positive Air Pressure (CPAP) for Obstructive Sleep Apnea (OSA)

ABSTRACT Obstructive sleep apneas are interruptions of sleep owing to a momentary choking off of the body’s air supply. These may occur hundreds of times during a night’s sleep, but are rarely consciously noticed by the patient. Their cumulative effects on health in the daytime can be disastrous in terms of accidents and worsening of chronic conditions. Up until the 1980s, the only cure was a permanent surgical opening in the trachea. This was superseded by the work of Australian pulmonologist, Colin Sullivan, who invented and developed a medical technology called Continuous Positive Air Pressure (CPAP) that would maintain respiration by inflating the airways so as to keep them open during sleep. Apnea continues to cause health problems and CPAP devices continue to provide solutions that help millions in the United States and tens of millions worldwide.

Flood risks to urban development on a coastal barrier landscape of Lekki Peninsula in Lagos, Nigeria

Lekki Peninsula, which is home to the nouveau riche, is one of the barrier islands of the barrier-lagoon system of the Lagos coastline. The peninsula has been undergoing rapid urbanization since 1980 in total disregard of its physical characteristics. This study assessed landscape dynamics in the peninsula from 1984 to 2014 and evaluated risks to development from potential storm surge flooding. The datasets included baseline data on geographical indicators/island characteristics, satellite imageries and ancillary data. Storm surge flooding hazards and areas at risk were assessed in a Planar GIS environment and with two-dimensional (2D) hydrodynamic simulation using the Cellular Automaton Evolutionary Slope and River (CAESAR) model. Results reveal that the Lekki Peninsula which was a green zone had grown from about 0.5% built-up area in 1984 to about 18% built-up area in 2014. This growth was due to urban expansion and occurred mostly in areas of ecological assets including mangroves, swamps and vegetation. The highest growth in built-up area occurred in Eti-Osa Local Government Area (LGA). Generally, the peninsula has a low-lying topography with 37% of its area lying between 0.5 m and 3 m while 63% is between 3 m and 5 m above mean sea level. Potential inundation simulation with the CAESAR model for selected storm surge levels reveal that at surge heights of 4 m and 5 m, 25% (mostly in Eti-Osa) and 37% respectively of the peninsula are flooded with the latter choking off Epe Expressway on both ends. Initial ingress of inundation occurred in Eti-Osa LGA. In comparison to Planar GIS water levels, the CAESAR model reflected more realistic flood extents. The base flood elevation (BFE) and design flood elevation (DFE) are recommended to improve the sustainability and resilience of future developments along with the recognition of natural processes in future policy and development of the peninsula.

Critical environmental justice and the state: a critique of Pellow

ABSTRACT How should movements for environmental justice orient themselves towards the state? Recent work in the environmental justice field critiques the legalistic basis of both environmental justice research and movement strategy based in juridical action, regulation, and advocacy within state institutions. Meanwhile, rightward-moving politics in the United States threatens to choke off even this limited strategy. Scholars have responded by urging movements to adopt a more skeptical strategic posture towards the state, one informed by an anarchist conception of states as uniformly repressive structures. This essay addresses the most systematic attempt at re-theorizing the state for these movements, David Pellow’s What is Critical Environmental Justice? While Pellow’s work to integrate intersectionality theory into environmental sociology has been recognized, less attention has been paid to his anarchist state theory, which implies an untenable strategy of movement withdrawal from politics. Environmental justice movements and scholarship need a state theory that allows for the possibility of action both against and within states. I introduce an alternative, ‘strategic-relational’ view of states, and suggest that changing structural patterns of environmental injustice will require re-thinking both the state and the ‘movement’ of environmental justice, as they are conventionally imagined.

Mud on the move.

Humans are reshaping the world9s mud supply, altering where—and how fast—it piles up. Thousands of years ago, our ancestors caused erosion rates to surge by starting to clear forests and plant crops, muddying lakes and rivers. Today, deforestation and urbanization are causing some rivers to carry more sediment, even as dams and efforts to curb erosion choke off sediment supplies to other waterways. Such changes, together with precipitation shifts driven by climate change, are leading to sometimes dramatic transformations in river deltas, coastal mud flats, and the amount of mud that ultimately collects at the bottom of the sea. Graphs, charts, and maps help tell this story.

1995–2005: A Decade of Innovation in Low Temperature Plasma and Its Applications

Scientific breakthroughs tend to come in spurts when unique societal, economical, and political circumstances conspire (knowingly or unknowingly) and create an environment ripe for creativity. The field of low temperature plasma (LTP) recently experienced such an upheaval, which this paper attempts to relate in some details. There have been “roadmap” papers published before, which look towards the future of the field, but all roads start somewhere and even “new” roads are often paved over older roads that were discovered and traveled by early pioneers. With the sharp decrease in funding for fusion research in the USA in the early 1990s the plasma science community was faced with a dire situation that threatened to choke off plasma physics advances. However, in the background and far from the visibility accorded to fusion research, a few laboratories were quietly engaged in innovative research that in due time revolutionized the LTP field and breathed new life into plasma science. Groundbreaking applications of LTP were investigated that until today constitute most of the LTP research activities. These innovations spanned a wide spectrum that included the invention of novel devices, improvement of existing ones, and the deployment of these devices to areas ranging from industrial to biomedical applications. These efforts turned out to have impactful scientific and societal implications. In this paper plasma sources and applications developed during this uniquely innovative decade are briefly discussed.

The Euro

The Euro

Experimental Model Validation of High Aspect Ratio Through-Hole Filling by Additive-Assisted Copper Electrodeposition

A multi-element, time-dependent model developed by Childers et al. [A.S. Childers, M.T. Johnson, J. Ramírez-Rico, and K.T. Faber, J. Electrochem. Soc., 160:3093-3102, 2013] for copper infiltration of large (∼50–200 µm diameter), high aspect ratio (∼60) through-hole channels was experimentally tested for validity. The model built on the work of Akolkar and Landau [R. Akolkar and U. Landau, J. Electrochem. Soc., 151:702-711, 2004] for copper deposition in micro-scale integrated circuitry. Childers’ model broadens the original by including the transport and adsorption of all electrolyte species - inhibitors, accelerators, and copper ions. The resulting model is tested experimentally with wood-derived biomorphic carbon materials. Results indicate that model predictions of premature pore choke off are in agreement with quantitative observations of copper infiltration and qualitative imaging of plated pore profiles. Low accelerator concentrations (0.002 ppm) yielded the highest quantity of copper infiltration without premature closure.

Knots "Choke Off" Polymers upon Stretching.

Long polymer chains inevitably get tangled into knots. Like macroscopic ropes, polymer chains are substantially weakened by knots and the rupture point is always located at the "entry" or "exit" of the knot. However, these phenomena are only poorly understood at a molecular level. Here we show that when a knotted polyethylene chain is tightened, most of the stress energy is stored in torsions around the curved part of the chain. The torsions act as "work funnels" that effectively localize mechanical stress in the immediate vicinity of the knot. As a result, the knot "chokes" the chain at its entry or exit, thus leading to bond rupture at much lower forces than those needed to break a linear, unknotted chain. Our work not only explains the weakening of the polymer chain and the position of the rupture point, but more generally demonstrates that chemical bonds do not have to be extensively stretched to be broken.

Brief of Amici Curiae Computer Scientists in Oracle America Inc., v. Google Inc., No. 2013-1021 (Fed. Cir.)

The freedom to reimplement and extend existing APIs has been the key to competition and progress in the computer field — both hardware and software. It made possible the emergence and success of many robust industries we now take for granted — such as industries for mainframes, PCs, peripherals (storage, modems, printers, sound cards, etc.), workstations/servers, and so on — by ensuring that competitors could challenge established players and advance the state of the art. Thus, excluding APIs from copyright protection has been essential to the development of modern computers and the Internet. For example, the widespread availability of diverse, cheap, and customizable personal computers owes its existence to the lack of copyright on the specification for IBM’s Basic Input/Output System (BIOS) for the PC. Companies such as Compaq and Phoenix reimplemented IBM’s BIOS without fear of copyright claims, making PC clones possible. And the open nature of APIs was essential to many modern computing developments, including those of operating systems such as UNIX, programming languages such as C, the Internet’s network protocols, and cloud computing.The uncopyrightable nature of APIs spurs the creation of software that otherwise would not have been written. When programmers can freely reimplement or reverse engineer an API without the need to negotiate a costly license or risk a lawsuit, they can create compatible software that the interface’s original creator might never have envisioned or had the resources to create. Moreover, compatible APIs enable people to switch platforms and services freely, and to find software that meets their needs regardless of what browser or operating system they use. Without the compatibility enabled by the open nature of APIs, consumers could be forced to leave their data behind when they switch to a new service. The freedom to reimplement APIs also helps rescue software or data — systems whose creators have either gone out of business or abandoned their product in the marketplace. Government entities and non-profits are especially susceptible to the orphan programs problem as they often cannot afford to upgrade and are left using legacy technologies for years or decades. When a popular computer platform or service shuts down, the ability to freely reimplement APIs protects the communities that rely on that software. The Federal Circuit's decision will determine whether or not APIs continue to remain open and thereby enable competition and innovation among software developers, and enable access to information and affordable technology for users. Should the Court reverse Judge Alsup’s well-reasoned opinion, it will hand Oracle and others the ability to monopolize any and all uses of systems that share their APIs. API creators would have veto power over any developer who wants to create a compatible program — regardless of whether she copies any literal code from the original API implementation. That, in turn, would upset the settled business practices that have enabled the American computer industries to flourish, and choke off many of the system’s benefits to consumers.* NYU law students Sam Zeitlin and Charlotte Slaiman assisted in the preparation of this brief.

Pricing Dynamics of Network Utilities in Developing Countries

This paper examines the pricing of a utility with an underdeveloped network facing a competitive fringe, short-run network adjustment costs, theft of service, and the threat of retaliatory government intervention that is increasing with the price it charges. Under a variety of plausible assumptions (in the context of developing countries) the utility will find its long-run profits enhanced if it exercises pricing restraint in the early stages of network development. These findings provide some useful insights for the design of post-privatization regulatory governance in developing countries where years of price controls have contributed to choking off investment in network expansion.

Migration within England and Wales and the Housing Market

Economic conditions exert a strong influence on regional migration. On the one hand, strong labour market conditions, as exemplified by low unemployment rates and high earnings, draw migrants into regions. On the other hand, strong housing market conditions can prevent movement since commuting may often be an alternative to migration. This can be thought of as giving rise to a migration equilibrium where high house prices choke off migration caused by strong labour market conditions. Expected capital gains in housing, however, can offset high levels of house prices, an effect ignored in previous literature. Migration can also be influenced more directly by the availability of housing relative to population without this being mediated through prices. This paper, by Gavin Cameron, John Muellbauer and Anthony Murphy, presents evidence on inter-regional net and gross migration between the regions of England and Wales that is broadly in accord with these expectations.

Hot Molecular Cores and the Formation of Massive Stars

It has been proposed that some hot molecular cores (HMCs) harbor a young embedded massive star, which heats an infalling envelope and accretes mass at a rate high enough to ``choke off'' an incipient HII region. This class of HMCs would mark the youngest phase known of massive star formation. In order to test this hypothesis, we model this type of object calculating the radiative transfer through a spherically symmetric dusty envelope infalling onto a central OB star, with accretion rates from 0.0006 to 0.001 solar masses per year. The dust thermal spectrum from infrared to radio wavelengths is derived and is compared with the observed fluxes of several hot cores which may be internally heated. We find that the data are best fitted using an envelope with the density distribution resulting from the collapse of a singular logatropic sphere, instead of that of a singular isothermal sphere. We conclude that several of these sources may be undergoing an intense accretion phase and find in all the cases that the accretion luminosity exceeds the stellar luminosity. We discuss the implications of this phase on the formation of massive stars.

Traffic restraint, road pricing and network equilibrium

Road pricing is now being advocated as an efficient means of managing traffic demand and of meeting other objectives, such as reducing the environmental impact of road traffic and improving public transport. This paper shows how a network toll pattern could be determined so as to reduce network travel demand to a desirable level. The demand between each origin-destination pair is described as a function of the generalized travel cost. When there is no toll charge, higher values of potential demand might cause congestion and queuing at bottleneck links of the road network. Queuing delay at saturated links may grow to choke off enough potential demand to reduce realized demand to the capacity of the network, thus leading to a queuing equilibrium where travel demand and travel cost match each other. In this paper, we first show how an elastic-demand network equilibrium model with queue could be used to determine this demand-supply equilibrium. We then seek a link toll pattern to remove the wasteful queuing delay, and/or restrain the realized demand to a desirable level to satisfy environment capacity constraints. We also show that the link toll pattern that could hold the traffic demand to a desirable level is not unique, a bi-level programming method is developed to select the best toll pattern among the feasible solutions based on pre-specified criteria.

Brain studies may alter long-held concepts about likely causes of some voice disorders

TWO VOICE DISORDERS long considered to be psychological problems, stuttering and spasmodic dysphonia, have been shown in many persons to have a neurophysiological basis. Investigators at the 155th national meeting of the American Association for the Advancement of Science, in San Francisco, described their findings, which are based on new analytic techniques. The research is being done at the Dallas Center for Vocal Motor Control, Callier Center for Communication Disorders, University of Texas at Dallas Health Science Center. Stuttering affects approximately 1 in 100 persons in the United States, and spasmodic dysphonia, in which spasms of the larynx choke off words as they are uttered, is thought to affect about a tenth as many. The technology employed to learn what's wrong with the brains, rather than the psyches, of persons with certain speech disorders includes magnetic resonance imaging (MRI), brain electrical activity mapping (BEAM), and single photon emission computerized tomography

Brain Studies May Alter Long-Held Concepts About Likely Causes of Some Voice Disorders

TWO VOICE DISORDERS long considered to be psychological problems, stuttering and spasmodic dysphonia, have been shown in many persons to have a neurophysiological basis. Investigators at the 155th national meeting of the American Association for the Advancement of Science, in San Francisco, described their findings, which are based on new analytic techniques. The research is being done at the Dallas Center for Vocal Motor Control, Callier Center for Communication Disorders, University of Texas at Dallas Health Science Center. Stuttering affects approximately 1 in 100 persons in the United States, and spasmodic dysphonia, in which spasms of the larynx choke off words as they are uttered, is thought to affect about a tenth as many. The technology employed to learn what's wrong with the brains, rather than the psyches, of persons with certain speech disorders includes magnetic resonance imaging (MRI), brain electrical activity mapping (BEAM), and single photon emission computerized tomography

The interdependence of electricity export markets an econometric examination of Quebec in a monopolistic setting

When a utility, such as that found in Quebec, Canada, can export electricity to two markets, the interdependence between export markets is critical in determining the profit-maximizing levels and prices of exports. In this paper a model is specified which verifies econometrically that Quebec in a monopolistic fashion adds a markup term to its marginal costs of export (to the Ontario and New Brunswick-United States markets). This model is then employed to examine the comparative static impact of a rise in variable costs of generating electricity within an export market. The resultant increase in exports to this market, the rise in export prices, and the choking off of exports to the other market is quantified.

The kinetics and mechanisms of reactions of human tooth enamel in buffered solutions of high fluoride concentrations

The experimental results were quantitatively compared with the theory based on a physical model representing the reaction and with the experiments involving synthetic hydroxyapatite discs. The experimental initial rates self-consistently compared well with the theoretical predictions. An analysis of the experimental initial rate data yielded a reaction constant, κ, for the reaction representing apatite dissolution and calcium fluoride precipitation. It is proposed that the value for κ is a result of both supersaturation with respect to calcium fluoride and undersaturation with respect to apatite at the apatite-calcium fluoride reaction sites. This finding is also consistent with the analysis of the experiments with synthetic apatite discs. Important similarities and significant differences were found between the experiments with the enamel sections and with synthetic apatite discs. The experiments with the synthetic apatite discs were reported to proceed “normally” as predicted by the physical model over the entire course of the reaction. In contrast to these findings, while the initial rates of the enamel-fluoride reaction were found to proceed relatively rapidly and according to the theoretical predictions, the rates at later times were drastically reduced. This “choking off” was observed to be most severe in the experiments at low pH and high fluoride concentrations, and little or no “choking oft” was observed at low fluoride concentrations and high pH.

Solar flares as resulting from the temporary interruption of energy flow to the corona: A case of hydromagnetic resonance

The hypothesis that solar flares may be caused by a choking off of the normal energy flux to the corona by the strong closed magnetic fields of a plage is examined. If the energy flux into a plage from the photosphere is of the order of 108 ergs/cm2 sec, and if a substantial fraction of this energy is carried in the form of Alfven waves, then the rate of dissipation of the waves is slower than the rate at which energy is injected. Since the waves must propagate along the magnetic field and cannot reenter the photosphere, they must remain within the plage; hence, the magnetic and kinetic energy in a small-scale motion (either waves, turbulence, or high-energy particles) must increase with time, eventually causing disruption of the volume when the small-scale energy density exceeds the energy in the mean field. It is believed that the unusually broad wings in the emission lines represent evidence of this phenomenon. The accumulation of waves is manifested as a resonance which occurs initially only at discrete locations in the magnetic field, but later is expected to involve the whole flare volume. The response of a typical volume of flare dimensions due to a trapping of the normal wave supply to the corona is studied through use of the virial equation. For magnetic fields typical of a plage, the region expands in a time scale of 102–103 sec, with a velocity in the neighborhood of 10–20 km/sec. Small-scale velocities within the region, however, have reached 100–300 km/sec, indicating that almost all the energy in the flare resides in small-scale forms. The energy density of the flare region exhibits a behavior much more explosive than the expansion rate. There is a rapid rise to maximum in 102 sec or less, and a slow subsequent decline taking about 103–104 sec due to the dilution of energy caused by expansion of the region. The predicted temporal behavior of the energy density coincides qualitatively with the light curves observed during flares, and it is suggested that the rise and decline of the energy density is to be associated with the optical flare. The total flare is defined as the time required for the energy density of the chromosphere and corona to return to the pre-flare state. During this time (about one hour) a large flare can derive the necessary 1032 ergs from normal photospheric energy output.