Holographic Holes and Differential Entropy

Recently, it has been shown by Balasubramanian et al. and Myers et al. that the Bekenstein-Hawking entropy formula evaluated on certain closed surfaces in the bulk of a holographic spacetime has an interpretation as the differential entropy of a particular family of intervals (or strips) in the boundary theory. We first extend this construction to bulk surfaces which vary in time. We then give a general proof of the equality between the gravitational entropy and the differential entropy. This proof applies to a broad class of holographic backgrounds possessing a generalized planar symmetry and to certain classes of higher-curvature theories of gravity. To apply this theorem, one can begin with a bulk surface and determine the appropriate family of boundary intervals by considering extremal surfaces tangent to the given surface in the bulk. Alternatively, one can begin with a family of boundary intervals; as we show, the differential entropy then equals the gravitational entropy of a bulk surface that emerges from the intersection of the neighboring entanglement wedges, in a continuum limit.Comment: 62 pages; v2: minor improvements to presentation, references adde

Lithium-Ion Battery Thermal Management Systems Using Flexible Graphite Heat Dissipators

Lithium-Ion batteries are used in a wide variety of devices over a broad range of powers. All batteries generate heat due to the internal resistance of the battery and entropic effects which is roughly proportional to amount of power being drawn from the cells. This heat can cause many problems in the operation of the battery including shortening the lifetime of the cells, reducing their power output, electrical imbalance between the cells due to non-uniform heating within a pack, and even the possibility of fire and explosion in extreme cases. Thermal management of the cells then becomes an important study. As technology progresses, higher power demands are put onto the battery packs. In addition, cells are routinely packed together as tightly as possible to conserve space. This increasing power density demands that heat be shared evenly between individual cells and ultimately removed from the battery pack. This research investigates the application of flexible graphite material in managing the heat production of lithium ion battery packs. The pack chosen for this study is a 10 cell, 36 volt pack consistent with the type found in modern hand-held rechargeable power tools. Three packs were designed including a control and two packs with different heat spreader geometries. The packs were constructed and instrumented with voltage leads on the individual cells and thermocouples. The packs were then subjected to a series of high-current charge/discharge cycles. Deviations in the voltages of the cells and the temperatures at several points within each pack were monitored as the batteries were cycled. When a iii predetermined exit condition based on a maximum limit on voltage and temperature spread within a pack, the experiment was concluded. While there was not enough data as of yet to detect a significant slowdown in voltage imbalance increase, there did appear to be a reduction in the rate of increase in temperature imbalance by using the graphite heat spreaders that should lead to an improvement in endurance as the experiment progresses.Center for Automotive Research - The Ohio State UniversityGrafTech InternationalA one-year embargo was granted for this item

A Response to Glaucon’s Challenge: The Sachs Problem and the Account of the Tyrannical Man

Few, if any, texts in philosophy have been more widely read and written on than Plato’s Republic. For many reasons philosophers have found this particular book to be extremely interesting. Of the many issues and arguments that appear in the Republic, Glaucon’s challenge is the most essential. Noticing the complexity and seriousness of the challenge, Socrates uses the entirety of the Republic to respond. The challenge deals with a very real and troublesome issue— whether one is happier when pursuing a life of justice or injustice. Philosophers have struggled with Glaucon’s challenge and Socrates’ response for a variety of reasons, but perhaps the most serious criticism is that Socrates does not completely answer the challenges posed by Glaucon and Adeimantus. David Sachs, professor of philosophy at Johns Hopkins and author of “A Fallacy in Plato’s Republic,” contends that Socrates’ response using the account of the Platonic soul is not relevant to the challenges due to its failure to meet multiple requirements. This well-known controversy is known as “The Sachs Problem.” The purpose of this paper will be to explore Glaucon’s Challenge and Socrates’ response in order to discover if, in fact, Socrates does truly answer the challenge. In order to do this, I will focus on Socrates’ response in Book IV, in which Socrates provides his account of the harmonious soul and on “The Sachs Problem,” which is intended to show that Socrates is unsuccessful in his attempt to dismiss the challenge. Finally, I plan to focus on Book IX, in which I believe Socrates provides his true response to the challenge that was issued by Glaucon and Adeimantus. Here, Socrates gives his account of the tyrannical soul and of his moral psychology. Ultimately, my aim is to discover if Sachs is successful in arguing that Socrates’ response to Glaucon’s Challenge is irrelevant or, on the other hand, if Sachs is mistaken and Socrates does provide a valid response to the challenge

The Stefan problem with variable thermophysical properties and phase change temperature

In this paper we formulate a Stefan problem appropriate when the thermophysical properties are distinct in each phase and the phase-change temperature is size or velocity dependent. Thermophysical properties invariably take different values in different material phases but this is often ignored for mathematical simplicity. Size and velocity dependent phase change temperatures are often found at very short length scales, such as nanoparticle melting or dendrite formation; velocity dependence occurs in the solidification of supercooled melts. To illustrate the method we show how the governing equations may be applied to a standard one-dimensional problem and also the melting of a spherically symmetric nanoparticle. Errors which have propagated through the literature are highlighted. By writing the system in non-dimensional form we are able to study the large Stefan number formulation and an energy-conserving one-phase reduction. The results from the various simplifications and assumptions are compared with those from a finite difference numerical scheme. Finally, we briefly discuss the failure of Fourier's law at very small length and time-scales and provide an alternative formulation which takes into account the finite time of travel of heat carriers (phonons) and the mean free distance between collisions.Comment: 39 pages, 5 figure

The one-dimensional Stefan problem with non-Fourier heat conduction

We investigate the one-dimensional growth of a solid into a liquid bath, starting from a small crystal, using the Guyer-Krumhansl and Maxwell-Cattaneo models of heat conduction. By breaking the solidification process into the relevant time regimes we are able to reduce the problem to a system of two coupled ordinary differential equations describing the evolution of the solid-liquid interface and the heat flux. The reduced formulation is in good agreement with numerical simulations. In the case of silicon, differences between classical and non-classical solidification kinetics are relatively small, but larger deviations can be observed in the evolution in time of the heat flux through the growing solid. From this study we conclude that the heat flux provides more information about the presence of non-classical modes of heat transport during phase-change processes.Comment: 29 pages, 6 figures, 2 tables + Supplementary Materia

Limits of behavioral control by temporally extended response -reinforcer relations

Three experiments were performed to determine the extent to which the behavior of rats can be controlled by response-reinforcer relations that are extended in time. In Experiment 1, bonus pellets delivered at the end of the session were contingent upon a shift in choice responding within the session. Experiment 2 examined control of aggregated responses by a delayed consequence over a much shorter time period than an entire session. The reinforcing efficacy of bonus pellets was assessed using a chained-schedule procedure. The relation between aggregated responses and a delayed reinforcing consequence was assessed several times per session and with shorter delays than in Experiment 1. Experiment 3 used an adjusting-delay procedure to assess whether differential reinforcer magnitudes have a differential effect on choice behavior when the delay between choice and subsequent reinforcement is equal for the two alternatives. The experiment was designed to determine the longest delay at which differential reinforcement is effective. Taken together, these three experiments were designed to determine the extent to which aggregated responses may be controlled by aggregated reinforcers or a single reinforcing event, and the extent to which a single response may be reinforced by its delayed consequence. Experiment 1 failed to produce reliable control of choice responding by the post-session consequence. Experiment 2 established control of responding by the delayed reinforcer, but such control was reliable for all rats only at delays of 40 s and less. Experiment 3 was unsuccessful in establishing discriminated choice performance by the large reinforcer, even at short delays, preventing the determination of the temporal limit of control by differential reinforcer magnitude. Overall, the results of this series of experiments suggest that the operant behavior of rats can be controlled by delayed consequences, but a finite limit to such control exists. It seems that reinforcers delayed on the order of several minutes or more are unlikely to control the behavior that produces them. Thus, response-reinforcer contiguity determines whether response-reinforcer correlations can control behavior

Organochlorines In Steller Sea Lions (Eumetopias Jubatus)

Thesis (Ph.D.) University of Alaska Fairbanks, 2009Existing populations of Steller sea lions (Eumetopias jubatus ) have declined precipitously over the last half-century. Investigations into the cause of this downward trend have focused on many different possible factors. Toxicity caused by the accumulation of organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT), has been demonstrated in marine mammals and was considered here as one possible factor that may have contributed to the decline of Steller sea lions or their failure to recover. The focus of this project was to investigate the relationship of contaminant loads to hormone levels, specifically thyroid hormones and cortisol in Steller sea lions. Two approaches were taken to this study. Firstly, baseline hormone concentrations were identified for the thyroid hormones, thyroxine (T 4) and triiodothyronine (T3), and cortisol. This involves comparison and extrapolation. Secondly, possible risk effects were examined by comparing levels of OCs in captive and free-ranging Steller sea lions to known effects in related species with known physiological thresholds. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. Cortisol concentrations were similar in male and female pups. Cortisol varied with age but when considered in regards to time of year when sampled, followed a seasonal pattern. Cortisol was elevated in fall months in captive sea lions (non-pups), which is similar to what is seen in other marine mammals and is likely associated with the annual molt. Male pups from Alaska had lower levels of SigmaPCBs and SigmaDDT when compared to male pups from Russia. Female pups from Alaska were significantly lower in SigmaPCBs than Russian female pups as were female pups for SigmaDDT levels between areas. Anywhere from 12 to 64% (depending on rookery) of Steller sea lion pups investigated for contaminants had concentrations of SigmaPCBs that are high enough to cause physiological problems. Concentrations in blood taken monthly for 2 years in three captive Steller sea lions were similar at any given sampling time and followed a seasonal pattern with levels significantly higher in the summer months of July to September and lower in the three month winter period January to March. Concentrations of OCs in blubber samples collected quarterly for the captive females followed an analogous pattern to blood samples but the captive male sea lion was considerably lower and declined over the study period. A significant relationship between blubber contaminants and lipids was noted in the three captive Steller sea lions. Even though OC contamination has not been hypothesized to be the primary factor that precipitated the population decline, there is a potential for these chemicals to have a negative effect on the health of free-ranging Steller sea lions. These data suggest that concentrations of OCs in Steller sea lions may be high enough to cause endocrine or reproductive dysfunction and could potentially impact fertility or fecundity. Therefore, OC contaminants can not be dismissed as a contributing source to either the decline or the failure to recover of the Steller sea lion population

The Idea of a Citizen: The Role of Higher Education Institutions in the Development of Citizens and an Exploration of Innovative Teaching Techniques to Aid in the Process

This work seeks to explain how institutions of higher education and political science educators within those institutions can develop students into citizens. Understanding the role of each (institution, educator, and student) within American democracy is important and the focus of this research. As the roles of each are demarcated, it becomes clear that higher education institutions and their political science educators have a unique ability to nurture students into citizens with a strong sense of civic purpose and understanding. The subsequent chapters in this work explore the use of experiential education and other innovative teaching methods to determine if students can be taught to be better citizens. Findings in those chapters suggest that traditional means of measuring engagement (i.e. social capital) may display some change (i.e. political and civic engagement), while other areas remain stagnant (i.e. religious participation, informal social connections, and trust). Also, the inclusion of innovative teaching techniques, like virtual reality, do increase bridging and bonding social capital, as well as empathy. Additionally, student responses to the experiences does yield important results that suggests students do positively evaluate their experiential education experience. This research suggests that political science educators have the ability to impact a student’s development as a citizen, but the educator must be willing to engage the student using methods not typically employed in classroom settings

The role of SIRT1 in skeletal muscle function and repair of older mice

Human skeletal muscle is a highly metabolic tissue necessary for mobility and coordination. Responsible for approximately one-fifth of the resting human metabolism, skeletal muscle is also an important regulator of metabolites like glucose and contributes to the regulation of body temperature. Although there is a gradual decline in muscle mass associated with aging, a certain percentage of the population suffer from severe muscle mass and strength deterioration, classified as sarcopenia (5-13% for people aged 60-70 years old, 11-50% for those 80 or older). Sarcopenia is linked to increased morbidity and mortality rates in the elderly population, while annual healthcare costs related to sarcopenia total in the millions of dollars. Because the prevalence of sarcopenia is expected to increase as a larger percentage of the population transitions into old age, it becomes imperative to understand the mechanisms of aging and longevity so that more effective interventions can be taken against age-related muscle deterioration. Our laboratory has previously demonstrated that resveratrol, a known activator of the protein sirtuin 1 (SIRT1), was effective in enhancing human muscle adaptations to exercise in elderly populations. A rich body of literature has long supported the association of SIRT1 with longevity, but there are still gaps in our knowledge of how SIRT1 expression affects the functionality and performance of muscles in aging skeletal muscle. Furthermore, SIRT1 has been shown to be important in the function of muscle satellite cells—which are muscle stem cells that are responsible for the majority of muscle regeneration. However, there is little knowledge about how SIRT1 expression affects muscle regeneration and performance after injuries. To investigate the role of SIRT1 in the performance of aging and injured skeletal muscle, we have employed the use of several transgenic mouse models with differential expression of SIRT1. Using these models, we performed a series of functional muscle tests, before and after cardiotoxin (CTX) induced muscle injuries, to identify and compare muscle aptitude and recovery capability. Skeletal muscle sections from each model were also taken to identify differences in muscle fiber size and type distribution. Additionally, both mitochondria and satellite cells were isolated from these models to assess whether SIRT1 expression contributed to differences in metabolic or regenerative capacities. We found that there was little functional difference between young wild-type (YWT, aged 20-30 weeks) and aged (80+ weeks old) wild-type (WT-80), SIRT1 overexpressor (OE-80), and SIRT1 muscle-knockout (MKO-80) mice in either force production or fatigability in the absence of intervention. Mice lacking SIRT1 expression in their satellite cells (SKO-80), however, did show a reduction in force production. Interestingly, both the OE-80 and MKO-80 mice showed significant (P \u3c 0.05) increases for p53 expression and reduced fatigability after recovering from injury, with the SIRT1 overexpressor model showing some signs of muscle potentiation. MKO-80 mice showed a significant increase in satellite cell regeneration (P \u3c 0.05) in vitro when analyzed with EdU, but no difference in proliferation when compared in vivo with BrdU, indicating that SIRT1 expression in adult skeletal muscle may be an early factor in limiting the proliferation of satellite cells. The mitochondrial and structural profiles of each model were found to have minimal differences. Overall, our data indicate that although SIRT1 expression in skeletal muscle does not seem to be necessary for normal muscle function after injury, it does exert some influence in muscle repair. Altering SIRT1 expression either positively or negatively in skeletal muscle improves muscle fatigability in injury-recovered muscles, indicating a potential regulatory role for SIRT1 in skeletal muscle, but not an essential requirement for its deacetylation activity. Interestingly, these alterations of SIRT1 expression in aged skeletal muscle also resulted in a significant increase of p53 expression, indicating a potential benefit for p53 expression to muscle recovery. SIRT1 expression in satellite cells was shown to be necessary to achieve normal contractile force, but did not affect fatigability in those muscle. Our work has indicated a complex role for SIRT1 in skeletal muscle regeneration. We have shown for the first time that SIRT1 is required in satellite cells for proper function, but is not essential for muscles to recover their functionality after injury. We have also provided evidence for a potentially new target for muscle recovery, the protein p53, and new insights into the role of SIRT1 in muscle recovery

Could Product Regulation Result in Less Hazardous Tobacco Products?

In 1964, the first Report of the Surgeon General of the United States concluded that cigarette smoking caused, or contributed to, many serious diseases, including lung cancer. Public health efforts to reduce tobacco use have had substantial success, but today, almost one-quarter of all Americans smoke and more than four hundred thousand Americans die yearly from tobacco use. It is clear that current public health efforts must be expanded. Despite our best efforts, it is also likely that many Americans will continue to start smoking, while others will be unable or unwilling to quit. Therefore, it is appropriate to ask what, if anything, can be done to reduce the harm suffered by those who continue to use tobacco