To investigate the neural substrates that underlie spontaneous musical performance, we examined improvisation in professional jazz pianists using functional MRI. By employing two paradigms that ...differed widely in musical complexity, we found that improvisation (compared to production of over-learned musical sequences) was consistently characterized by a dissociated pattern of activity in the prefrontal cortex: extensive deactivation of dorsolateral prefrontal and lateral orbital regions with focal activation of the medial prefrontal (frontal polar) cortex. Such a pattern may reflect a combination of psychological processes required for spontaneous improvisation, in which internally motivated, stimulus-independent behaviors unfold in the absence of central processes that typically mediate self-monitoring and conscious volitional control of ongoing performance. Changes in prefrontal activity during improvisation were accompanied by widespread activation of neocortical sensorimotor areas (that mediate the organization and execution of musical performance) as well as deactivation of limbic structures (that regulate motivation and emotional tone). This distributed neural pattern may provide a cognitive context that enables the emergence of spontaneous creative activity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The need for electrical energy storage (EES) is being driven by the deployment of increasing amounts of intermittent renewable energy resources. In addition to their fuel flexibility, high ...efficiency, scalability, and long-term cost outlook, reversible (regenerative) solid oxide cell (rSOC) systems have the potential for round-trip efficiencies competitive with the other available energy storage technologies. Accordingly, the focus of the current study is to investigate modeling methods for high temperature rSOCs in order to facilitate future endeavors related to establishing optimal operating conditions and system designs. Previously developed solid oxide fuel cell (SOFC) and solid-oxide electrolytic cell (SOEC) models are integrated to form a general rSOC model. The model is first calibrated and validated based on the available experimental data in the extant literature. The validation results show that the fitting parameters extracted from the calibration study can precisely simulate the cell behavior under various operating conditions. The effects of key operating parameters, such as temperature, gas composition and fuel utilization, on the voltage–current density performance characteristic and thermoneutral voltage are then investigated. It is also observed that the total electrochemical losses of the cell can be significantly different in each operating mode (fuel cell and electrolyzing) under certain operating conditions. Advantages of pressurized operation on thermal management are also discussed.
•A previously developed cell model is modified for reversible solid oxide cell operation.•Model calibration and validation are performed for planar, electrode-supported rSOCs.•Effects of gas composition, pressure, and temperature on cell performance are investigated.•Pressurized operation enhances cell performance and promotes the methanation reaction.•Electrochemical cell losses can differ significantly in fuel cell and electrolysis modes.
There is general agreement that the diet of early hominins underwent dramatic changes shortly after the appearance of stone tools in the archaeological record. It is often assumed that this change is ...associated with dietary expansion to incorporate large mammal resources. Although other aspects of the hominin diet, such as aquatic or vegetal resources, are assumed to be a part of hominin subsistence, identifying evidence of these adaptations has proved difficult. Here we present a series of analyses that provide methodological support for the inclusion of aquatic resources in hominin dietary reconstructions. We suggest that bone surface modifications in aquatic species are morphologically distinguishable from bone surface modifications on terrestrial taxa. We relate these findings to differences that we document in the surface mechanical properties of the two types of bone, as reflected by significant differences in bone surface microhardness values between aquatic and terrestrial species. We hypothesize that the characteristics of bone surface modifications on aquatic taxa inhibit the ability of zooarchaeologists to consistently diagnose them correctly. Contingently, this difficulty influences correspondence levels between zooarchaeologists, and may therefore result in misinterpretation of the taphonomic history of early Pleistocene aquatic faunal assemblages. A blind test using aquatic specimens and a select group of 9 experienced zooarchaeologists as participants was designed to test this hypothesis. Investigation of 4 different possible explanations for blind test results suggest the dominant factors explaining patterning relate to (1) the specific methodologies employed to diagnose modifications on aquatic specimens and (2) the relative experience of participants with modifications on aquatic bone surfaces. Consequently we argue that an important component of early hominin diets may have hitherto been overlooked as a result of (a) the paucity of referential frameworks within which to identify such a component and (b) the inability of applied identification methodologies to consistently do so.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The use of regenerative, high temperature solid oxide cells (SOCs) as energy storage devices has the potential for round-trip efficiencies that are competitive with other storage technologies. The ...focus of the current study is to investigate regenerative SOC operation (i.e., working in both fuel cell and electrolysis modes) through a combination of modeling and numerical simulation. As an intermediate step, this paper focuses on the electrolysis mode and presents a dynamic cell model that couples the reversible electrochemistry, reactant chemistry, and the thermo-fluidic phenomena inside a cell channel. The model is calibrated and validated using available experimental and numerical data for button cells, single cells, and multi-cell stacks supplied with either steam or syngas. Parametric studies are also performed to show how the investigated parameters affect model validity. The results show that the present model can accurately simulate the electrolytic cell behavior, especially in the low current range, which is a favored operating point in practical systems. It is observed that improvements in stack-level model precision require further investigation to better represent the contact resistance of the stack components and to improve the estimation of the activation polarization throughout the operating envelope. It is also concluded that the CO2 electrochemical reaction can be neglected when the concentration of the steam supplied to the cell is high enough to support the water–gas shift reaction.
•Steady-state cell model is developed for solid oxide electrolysis cells.•Model validation is performed for steam and steam/CO2 gas mixtures at high and medium temperatures.•The contact resistance of the cell/stack components is an important simulation parameter.•Accurate evaluation of the activation polarization is an important issue in the modeling of SOECs.•CO2 electrochemical reaction is negligible when the feedstock H2O is high to support WGS reaction.
We develop a general framework for quantifying the many different contributions to the noise budget of an image made with an array of dishes or aperture array stations. Each noise contribution to the ...visibility data is associated with a relevant correlation timescale and frequency bandwidth so that the net impact on a complete observation can be assessed when a particular effect is not captured in the instrumental calibration. All quantities are parameterised as function of observing frequency and the visibility baseline length. We apply the resulting noise budget analysis to a wide range of existing and planned telescope systems that will operate between about 100 MHz and 5 GHz to ascertain the magnitude of the calibration challenges that they must overcome to achieve thermal noise limited performance. We conclude that calibration challenges are increased in several respects by small dimensions of the dishes or aperture array stations. It will be more challenging to achieve thermal noise limited performance using 15 m class dishes rather than the 25 m dishes of current arrays. Some of the performance risks are mitigated by the deployment of phased array feeds and more with the choice of an (alt,az,pol) mount, although a larger dish diameter offers the best prospects for risk mitigation. Many improvements to imaging performance can be anticipated at the expense of greater complexity in calibration algorithms. However, a fundamental limitation is ultimately imposed by an insufficient number of data constraints relative to calibration variables. The upcoming aperture array systems will be operating in a regime that has never previously been addressed, where a wide range of effects are expected to exceed the thermal noise by two to three orders of magnitude. Achieving routine thermal noise limited imaging performance with these systems presents an extreme challenge. The magnitude of that challenge is inversely related to the aperture array station diameter.
Does fiscal policy have large and qualitatively different effects on the economy when the nominal interest rate is zero? An emerging consensus in the New Keynesian (NK) literature is that the answer ...to this question is yes. Evidence presented here suggests that the NK model׳s implications for fiscal policy at the zero bound may not be all that different from its implications for policy away from it. For a range of empirically relevant parameterizations, employment increases when the labor tax rate is cut and the government purchase multiplier is less than 1.05.
•We show that it matters how one solves the New Keynesian model at the zero lower bound (ZLB).•The nonlinear solution exhibits new types of ZLB equilibria that cannot occur using a loglinearized solution.•Fiscal multipliers are small and orthodox at the ZLB for a large and plausible set of parameterizations of the model.•The New Keynesian model can be used to make a case for supply-side fiscal stimulus at the ZLB.•In situations where a labor tax rate cut increases employment, the government purchase multiplier is about one or less.
This paper presents a techno-economic analysis of biogas-fueled solid oxide fuel cell (SOFC) systems for combined heat and power (CHP) applications in wastewater treatment facilities (WWTFs). ...SOFC-CHP systems ranging from 300 kWe to 6 MWe in electric power capacity are explored in terms of their performance and life cycle costs. Representative biogas feedstock is established from compositional data for a large wastewater reclamation facility in Denver, Colorado. A steady-state SOFC-CHP system model is developed with Aspen Plus for the integration with small (640 kWLHV), medium (2.97 MWLHV) and large (11.92 MWLHV) biogas sources. The proposed SOFC system concept includes anode gas recirculation, a biogas pretreatment system, and a waste heat recovery unit. The system offers a net electrical efficiency of 51.6% LHV and a net CHP efficiency of 87.5% LHV. The effect of operating parameters on system efficiency is investigated with a parametric study. The economic performance is evaluated with the levelized costs of electricity (COE) and heat (COH). The results are compared with the COE from reciprocating engine, gas turbine, microturbine, molten carbonate fuel cell technologies, and grid electricity prices. The influence of economic parameters and stack operating parameters on the levelized COE is also presented.
► SOFC systems fueled with biogas offer net electrical efficiencies near 52% (LHV). ► Estimated installed costs range from 3590 $/kW to 5780 $/kW (large- to small-scale). ► SOFC-based cost of electricity is competitive with grid-pricing at 5–8 ¢/kW h. ► SOFCs for biogas applications are competitive with other cogeneration technologies. ► Economic viability also depends on biogas quality, utility pricing, and incentives.
Mammary epithelial cells transition between periods of proliferation and quiescence during development, menstrual cycles, and pregnancy, and as a result of oncogenic transformation. Utilizing an ...organotypic 3D tissue culture model coupled with quantitative metabolomics and proteomics, we identified significant differences in glutamate utilization between proliferating and quiescent cells. Relative to quiescent cells, proliferating cells catabolized more glutamate via transaminases to couple non-essential amino acid (NEAA) synthesis to α-ketoglutarate generation and tricarboxylic acid (TCA) cycle anaplerosis. As cells transitioned to quiescence, glutamine consumption and transaminase expression were reduced, while glutamate dehydrogenase (GLUD) was induced, leading to decreased NEAA synthesis. Highly proliferative human tumors display high transaminase and low GLUD expression, suggesting that proliferating cancer cells couple glutamine consumption to NEAA synthesis to promote biosynthesis. These findings describe a competitive and partially redundant relationship between transaminases and GLUD, and they reveal how coupling of glutamate-derived carbon and nitrogen metabolism can be regulated to support cell proliferation.
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•Proliferating cells catabolize glutamate via transaminases to synthesize NEAAs•Glutamate dehydrogenase is induced in quiescence, and NEAA synthesis is reduced•Highly proliferative breast tumors have high transaminase and low GLUD expression•Transaminases and GLUD display a competitive and partially redundant relationship
Using a 3D tissue culture model, Coloff et al. identify differences in glutamate utilization in proliferating and quiescent mammary epithelial cells. These studies demonstrate that highly proliferative normal and breast cancer cells couple glutamine-derived carbon and nitrogen metabolism by suppressing glutamate dehydrogenase and synthesizing NEAAs via transaminases.
A model for high temperature co-electrolysis (HTCE) of carbon dioxide and water using solid oxide electrolytic cells (SOEC) for syngas production and subsequent conversion to liquid fuels by a ...Fischer–Tropsch (F–T) process is presented. The SOEC model is guided by experimental data from the literature, and the model is employed to explore the effect of temperature, pressure, and feedstock composition on syngas composition exiting the SOEC. The syngas is converted in a slurry bubble column F–T synthesis reactor in which the model approach of a once-through conversion of carbon monoxide is chosen, and the distribution of hydrocarbon products is determined by the Anderson–Schulz–Flory model. The overall system efficiency for liquid hydrocarbon fuels produced from electrical energy is found to be 54.8% HHV (51.0%-LHV). It is determined that operating the SOEC at low pressure (1.6 bar) versus higher pressure (5 bar) results in an efficiency gain of 2.6%. The economics of the production plant are evaluated for variations in electricity feedstock costs and operating capacity factors. The liquid fuels production costs range from 4.4 $/GGE to 15.0 $/GGE for electricity prices of 0.02 $/kWh to 0.14 $/kWh and a plant capacity factor of 90% to 40%, respectively.
▸ Detailed modeling of both SOEC operation and F–T synthesis and distillation is presented. ▸ SOEC syngas production and system performance sensitivities to operating pressure are explored. ▸ Results indicate lower pressure SOEC operation is favored for F–T synthesis. ▸ Fuel production efficiencies of 50.1%-HHV are reported and detailed economic costing is performed. ▸ Liquid fuels production cost estimates are made and range from 3.3 $/GGE to 18.3 $/GGE.
Half of U.S. 50-year-olds will experience a nursing home stay before they die, and one in ten will incur out-of-pocket long-term care expenses in excess of $200,000. Surprisingly, only about 10% of ...individuals over age 62 have private long-term care insurance (LTCI) and LTCI takeup rates are low at all wealth levels. We analyze the contributions of Medicaid, administrative costs, and asymmetric information about nursing home entry risk to low LTCI takeup rates in a quantitative equilibrium contracting model. As in practice, the insurer in the model assigns individuals to risk groups based on noisy indicators of their nursing home entry risk. All individuals in frail and/or low-income risk groups are denied coverage because the cost of insuring any individual in these groups exceeds that individual's willingness-to-pay. Individuals in insurable risk groups are offered a menu of contracts whose terms vary across risk groups. We find that Medicaid accounts for low LTCI takeup rates of poorer individuals. However, administrative costs and adverse selection are responsible for low takeup rates of the rich. The model reproduces other empirical features of the LTCI market including the fact that owners of LTCI have about the same nursing home entry rates as non-owners.
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