Graphene Spin Transistor

Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been proposed as ideal materials for spin conduction[1-7]; they have long electronic mean free paths[8] and small spin-orbit coupling[9], hence are expected to have very long spin-scattering times. In addition, spin injection and detection in graphene opens new opportunities to study exotic electronic states such as the quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge states[12] in graphene ribbons. Here we perform the first non-local four-probe experiments[13] on graphene contacted by ferromagnetic Permalloy electrodes. We observe sharp switching and often sign-reversal of the non-local resistance at the coercive field of the electrodes, indicating definitively the presence of a spin current between injector and detector. The non-local resistance changes magnitude and sign quasi-periodically with back-gate voltage, and Fabry-Perot-like oscillations[6,14,15] are observed, consistent with quantum-coherent transport. The non-local resistance signal can be observed up to at least T = 300 K

A Framework for Exchange Rate Policy in Korea

The monetary policy and exchange rate regime that served Korea well for many years ended in crisis in 1997. The regime that collapsed was characterized by a tightly managed nominal exchange rate and domestic financial markets that were controlled by the government and largely closed to international transactions. The practical question for authorities over the next few years is what monetary and exchange rate regime will best promote the objectives of maintaining economic and financial stability as financial markets are liberalized. Our basic proposal is that the powerful policy tool, interest rate policy, be used to attain a "flexible" inflation target. Flexibility in this context means that the authorities also care about short-run fluctuations in domestic output and employment. The less powerful policy tool, sterilized intervention in the foreign exchange market, would be used to limit day to day changes in exchange rates. We argue that the government should continue to be an important participant in the foreign exchange market but not attempt to establish a level for the exchange rate. Our proposal will involve intervention that is triggered by exchange rate volatility but constrained by an announced target for the government's overall net foreign asset position. The objective of this regime is to allow the government to participate in the foreign exchange market in a way that contributes to economic stability and promotes the development of the private sector's participation in foreign exchange and financial markets.monetary policy, exchange rate regime, Korea, government

Returns to Skill and Teacher Wage Premiums: What Can We Learn By Comparing the Teacher and Private Sector Labor Markets?

Estimates the wage differences between public school teachers and other professions over time by gender, advanced degree, major, college quality, and technical and academic skills. Explores the incentives needed to attract and retain effective teachers

Queen of Spades

Semblance—or parody—is, of course, the operative word when considering a text that strives to be subversive of both form (the “anti-realism” of minor literature) and social function. Regarding the latter, as stated before, my goal in the text is the reverse of the traditional moral fable’s: implanting a desire in readers to experience firsthand the world of risk as a means to live in a more vital way, outside the text, whether through gambling or another form of chance-taking. Uncertainty is troubling, unsettling, but it is also mysterious and enlivening—this is what gamblers, acolytes at the altar of luck, understand in the final analysis

Obesity, intergenerational programming, and epigenetics: emerging concepts and challenges

One of the most important medical and public health issues of today is obesity, defined as abnormal and excess fat accumulation. Obesity is linked to many health problems including metabolic syndrome (MS), hypertension, type II diabetes mellitus (T2DM), and cardiovascular disease (CVD). Recently, the incidence of these conditions has surged to epidemic proportions, especially in Western societies. Research has also linked obesity to cancer and osteoarthritis. Preventing, diagnosing, and treating obesity is challenging. The diagnosis of obesity is often unclear when it is made with generalized criteria such as the Body Mass Index (BMI). Obesity interventions generally include the often difficult lifestyle change to healthy diets and adequate exercise, which depends heavily upon patient compliance and discipline. Today's society is pushing for the discovery of a shortcut or of a "magic pill" to cure obesity. Consequently, many studies aim to identify therapeutic targets. The majority of current obesity research is focused on discovering and revealing the underlying mechanisms and genetic risk factors. Certain stages of development, such as childhood, are especially susceptible times to be exposed to stressors that lead to obesity. A developing concept is the intergenerational transmission of risk of obesity through epigenetics. Epigenetics is the study of the heritable changes in gene regulation and expression not caused by mutations or changes in DNA sequence. A person's genes may increase or decrease his or her susceptibility to obesity. In addition to genetic inheritance, parents may pass non-genetic alterations to their children. Changes can be mediated through methylation of deoxyribonucleic acids (DNA) and modifications to histones. These epigenetic changes may alter gene expression patterns and "program" offspring towards developing chronic metabolic disease. Many models have begun to show the effects of environmental perturbations on individuals and on several generations of future descendants. This review will analyze the current literature on obesity and evaluate this rapidly evolving field. Current obesity preventions and treatments will be surveyed. In addition, the relative impact of different contributors to obesity risk will be examined. The crossover between obesity and epigenetics may provide a deeper understanding of disease risk and developmental origins. Future directions of study will be proposed such as large-scale prospective studies to further characterize intergenerational transmission of risk

Methane release on Early Mars by atmospheric collapse and atmospheric reinflation

A candidate explanation for Early Mars rivers is atmospheric warming due to surface release of H$_2$ or CH$_4$ gas. However, it remains unknown how much gas could be released in a single event. We model the CH$_4$ release by one mechanism for rapid release of CH$_4$ from clathrate. By modeling how CH$_4$-clathrate release is affected by changes in Mars' obliquity and atmospheric composition, we find that a large fraction of total outgassing from CH$_4$ clathrate occurs following Mars' first prolonged atmospheric collapse. This atmosphere-collapse-initiated CH$_4$-release mechanism has three stages. (1) Rapid collapse of Early Mars' carbon dioxide atmosphere initiates a slower shift of water ice from high ground to the poles. (2) Upon subsequent CO$_2$-atmosphere re-inflation and CO$_2$-greenhouse warming, low-latitude clathrate decomposes and releases methane gas. (3) Methane can then perturb atmospheric chemistry and surface temperature, until photochemical processes destroy the methane. Within our model, we find that under some circumstances a Titan-like haze layer would be expected to form, consistent with transient deposition of abundant complex abiotic organic matter on the Early Mars surface. We also find that this CH$_4$-release mechanism can warm Early Mars, but special circumstances are required in order to uncork 10$^{17}$ kg of CH$_4$, the minimum needed for strong warming. Specifically, strong warming only occurs when the fraction of the hydrate stability zone that is initially occupied by clathrate exceeds 10%, and when Mars' first prolonged atmospheric collapse occurs for atmospheric pressure > 1 bar.Comment: Accepted by Planetary and Space Scienc

A Systematic Retrieval Analysis of Secondary Eclipse Spectra III: Diagnosing Chemical Disequilibrium in Planetary Atmospheres

Chemical disequilibrium has recently become a relevant topic in the study of the atmospheres of of transiting extrasolar planets, brown dwarfs, and directly imaged exoplanets. We present a new way of assessing whether or not a Jovian-like atmosphere is in chemical disequilibrium from observations of detectable or inferred gases such as H_2 O, CH_4, CO, and H _2. Our hypothesis, based on previous kinetic modeling studies, is that cooler atmospheres will show stronger signs of disequilibrium than hotter atmospheres. We verify this with chemistry-transport models and show that planets with temperatures less than ~ 1200 K are likely to show the strongest signs of disequilibrium due to the vertical quenching of CO, and that our new approach is able to capture this process. We also find that in certain instances a planetary composition may appear in equilibrium when it actually is not due to the degeneracy in the shape of the vertical mixing ratio profiles. We determine the state of disequilibrium in eight exoplanets using the results from secondary eclipse temperature and abundance retrievals. We find that all of the planets in our sample are consistent with thermochemical equilibrium to within 3-sigma. Future observations are needed to further constrain the abundances in order to definitively identify disequilibrium in exoplanet atmospheres

The atmosphere and ionosphere of Io

A variety of models for Io's atmosphere, ionosphere, surface, and environment are developed and discussed in the context of recent observational data. The sodium emission detected by Brown appears to require a collisional excitation process in Io's atmosphere, and the extended sodium emission measured by Trafton et al. may require scattering of the planetary radiation by an extended sodium cloud. The sodium is presumably present initially in bound form on Io's surface and may be released by the sputtering mechanism suggested by Matson et al. The ionosphere detected by the radio occultation experiment on Pioneer 10 could be attributed to photoionization of atmospheric sodium if Io's atmosphere could sustain significant vertical motions, of order 1 s^(-1) directed up during the day, down at night. Vertical motions of this magnitude could be driven by condensation of atmospheric NH_3. The total density of gas at Io's surface appears to lie in the range 10^(10)-10^(12) molecules cm^(-3). Corpuscular ionization could play an additional role for the Ionosphere. In this case the satellite should exhibit an exceedingly bright, ~ 10 kR, airglow at Lɑ. The incomplete hydrogen torus observed by Judge and Carlson in the vicinity of Io requires a large supply of hydrogen from the satellite's atmosphere. The escape flux should be of order 10^(11) cm^(-2) s^(-1) and could be maintained by photolysis of atmospheric NH_3. The observed geometry of the hydrogen torus appears to require a surprisingly short lifetime, ~ 10^5 s, for neutral hydrogen near Io's orbit, and may indicate the presence of a large flux, ~ 10^9 cm ^(-2) s^(-1), of low-energy protons in Jupiter's magnetosphere. Implications of the hydrogen torus for the energy and mass balance of Jupiter's magnetosphere are discussed briefly, and observational programs are identified which might illuminate present uncertainties in our understanding of Io

Dynamics between Direct Industrial Real Estate and the Macroeconomy: An Empirical Study of Hong Kong

Pricing of direct industrial real estate (DIRE) has long been under-researched due to the paucity of analysable data. Compared to other types of real estate, DIRE has often been regarded as more inefficient because of information asymmetry amongst market players stemming from a lack of market transparency. Therefore, pricing of DIRE usually does not follow a random walk and should be more predictable than other types of real estate. Along this line of reasoning, this study empirically investigates the causal relationships between the price-to-rent ratio of DIRE and macroeconomic attributes using cointegration and causality techniques. More specifically, we employ data on the market of Hong Kong to investigate the lead-lag relationships between the price-to-rent ratio of DIRE and a wide spectrum of macroeconomic and financial indicators, including inflation, money supply, national income, exchange rates, performance of housing market and other economic indicators specific to the industrial sector. The results of our statistical tests reveal significant evidence that DIRE is generally moving in syncs with other segments of the economy over time in terms of long-term cointegration. Further, DIRE tends to lag behind the overall macroeconomy in terms of Granger causation with the price-to-rent ratio exhibiting varying lengths of time lag with the macroeconomic determinants. The findings of the study carry important implications for informing property valuation practices and industrial land policy, particularly in designing urban revitalization programmes aimed at optimising industrial land use

Lead-lag relationship between the price-to-rent ratio and the macroeconomy: An empirical study of the residential market of Hong Kong

The price-to-rent (PtR) ratio is one of the most commonly used indicators to assess housing market conditions by policy makers and real estate practitioners. It is often employed as an economic barometer to detect whether a housing bubble exists and determine whether the property market has become unaffordable relative to historical trends. Despite a plethora of research studies on the PtR ratio in the housing literature, relatively little is known about its long-term dynamics with macroeconomic and financial determinants. By utilising time series data on the Hong Kong residential property market, this study examines the cointegration and causal relationships between a wide spectrum of macroeconomic indicators and the PtR ratios of housing segments of different tiers which comprise different socioeconomic groups of homebuyers and investors. The results point towards market compartmentalisation, in the sense that the PtR ratios of the housing submarkets respond to changes in macroeconomic fundamentals in a differential manner. For instance, the PtR ratios of housing segments with a greater proportion of owner-occupiers are statistically less y correlated with investment-related macroeconomic attributes, such as foreign direct investment and equity market performance. On the other hand, the pricing of large-sized housing units in prime locations, generally favoured by investors from mainland China, are found to be Granger-caused by the exchange rate of the Chinese Yuan to the Hong Kong dollar