A tight-binding model for the excitonic band structure of a one-dimensional molecular chain: UV-Vis spectra, Zak phase and topological properties

Recently organic optics becomes a hot topic due to the rapid development of organic light-emitting diodes, organic solar cells, and organic photon detectors. The optical spectra of the molecular semiconductors are difficult to solve an model from first-principles because (i) the very large number of atoms in a unit cell and (ii) the accurate theoretical excited state is still under development. Here we present a tight-binding model of an exciton band structure in a molecular chain. We take into account the intra-molecule and charge-transfer excitation within a molecular dimer in a unit cell, then we apply the tight-binding model by including the coupling between two types of excitations. We not only found that our calculations can explain a body of UV-Vis optical spectra of transition-metal phthalocyanines, but also a one-dimensional excitonic topological band structure if we fine-tune the couplings in a dimerized molecular chain. We have found a large space to obtain the topological Zak phase in the parameter space, in which there is a simple linear relationship between the hopping integrals between cells and within cell.Comment: 5 pages, 5 figure

Joint Network and Gelfand-Pinsker Coding for 3-Receiver Gaussian Broadcast Channels with Receiver Message Side Information

The problem of characterizing the capacity region for Gaussian broadcast channels with receiver message side information appears difficult and remains open for N >= 3 receivers. This paper proposes a joint network and Gelfand-Pinsker coding method for 3-receiver cases. Using the method, we establish a unified inner bound on the capacity region of 3-receiver Gaussian broadcast channels under general message side information configuration. The achievability proof of the inner bound uses an idea of joint interference cancelation, where interference is canceled by using both dirty-paper coding at the encoder and successive decoding at some of the decoders. We show that the inner bound is larger than that achieved by state of the art coding schemes. An outer bound is also established and shown to be tight in 46 out of all 64 possible cases.Comment: Author's final version (presented at the 2014 IEEE International Symposium on Information Theory [ISIT 2014]

Anticipations of Foreign Exchange Volatility and Bid-Ask Spreads

The paper studies the effect of the market's perceived exchange rate volatility on bid-ask spreads. The anticipated volatility is extracted from currency options data. An increase in the perceived volatility is found to widen bid-ask spreads. The direction of the effect is consistent with an option model of the spread, but the magnitude is smaller. An increase in trading volume of spot exchange rates also widens the spread. The omission of the trading volume, however, does not bias the estimate of the effect of the volatility on the spreads. Although the spread-volatility relation implied by the option model of the spread is close to linear, some form of nonlinearity can still be detected from the data.

Corruption in economic development - beneficial grease, minor annoyance, or major obstacle?

The author reviews the overwhelming statistical evidence that countries with high levels of corruption experience poor economic performance. Corruption hinders economic development by reducing domestic investment, discouraging foreign direct investment, encouraging overspending in government, and distorting the composition of government spending (away from education, health, and infrastructure maintenance toward less efficient but more manipulable public projects). The World Bank and the International Monetary Fund, among others, define corruption as"the abuse of public office for private gains". Whenever a public office is abused, a public function or objective is set aside and compromised. Only if a public function is unproductive are policy goals unharmed by corruption. But one often hears that bribery greases the machinery of commerce, so the author studied the evidence - which clearly rejects the hypothesis. Culture shapes the difference between a"bribe"and a"gift"but culturally induced differences seem small. There is no evidence to support the notion that corruption in Asia, including East Asia, entails lesser consequences. Corruption can be symptomatic of many social ills so the fight against it must be multifaceted. Laws and law enforcement are indispensable, but countries serious about fighting corruption should also reform government's role in the economy, especially in areas that (by giving officials discretionary power) are hotbeds of corruption. Recruiting and promoting civil servants on the basis of merit and paying them a salary competitive with similar jobs in the private sector helps attract moral, high-quality civil servants. International pressure on corrupt countries, and also to criminalize the bribing of foreign officials by multinational firms, can be useful. But anti-corruption campaigns cannot succeed without reforming domestic institutions in the corrupt countries.Poverty Monitoring&Analysis,Corruption&Anitcorruption Law,Legal Products,Decentralization,Public Sector Corruption&Anticorruption Measures,National Governance,Governance Indicators,Legal Products,Corruption&Anitcorruption Law,Public Sector Corruption&Anticorruption Measures

Preen Gland-Secreted Alkanols Enhance Male Attractiveness in Parrots

The skin glands are widely used in pheromone production throughout the vertebrate worlds. Growing evidences show that birds also have chemical communication, but the uropygial (also called preen or oil) glands, serving as only specialized skin glands of birds, have no sex pheromones characterized. Here, by combining GC-MS analysis and bioassay, we show with the budgerigar, Melopsittacus undulatus, that birds can used the preen gland-secreted volatiles (a blend of octadecanol, nonadecanol and eicosanol for male budgerigars) spread over body plumage when preening to convey sex information. Here, we first report the avian pheromones derived from the uropyginal gland and suggests that the gland has broader implications than previously known (e.g. plumage waterproofing and reflectance in sexual behaviour of birds