We examine the effects of transit, documentation, and ports and customs delays on Africa’s exports. We find that transit delays have the most economically and statically significant effect on exports. A one day reduction in inland travel times leads to a 7 percent increase in exports. Put another way, a one day reduction in inland travel times translates into 1.5 percentage point decrease in al...

This paper proposes a fast but effective user-guided colorization algorithm. The main difficulty with colorization is its intensive computational cost. And the color sometimes diffuses from one region to others. We make full use of the information given by the gray-scale images, including the edge, gradient and gradient direction, to propagate color over regions from the user’s scribbles. We in...

We show that causality constrains the sign of quartic Riemann corrections to the Einstein-Hilbert action. Our constraint constitutes a restriction on candidate theories of quantum gravity.

This study examined whether phrasal prosody can impact toddlers' syntactic analysis. French noun-verb homophones were used to create locally ambiguous test sentences (e.g., using the homophone as a noun: [le bébésouris] [a bien mangé] - [the baby mouse] [ate well] or using it as a verb: [le bébé] [sourità sa maman] - [the baby] [smiles to his mother], where brackets indicate prosodic phrase bou...

We argue that extended technicolor augmented with topcolor requires that all mixing between the third and the first two quark generations resides in the mixing matrix of left–handed down quarks. Then, the B̄d–Bd mixing that occurs in topcolor models constrains the coloron and Z ′ boson masses to be greater than about 5 TeV. This implies fine tuning of the topcolor couplings to better than 1%. bu...

Indoleamine 2,3-dioxygenase 1 (IDO1) metabolizes L-tryptophan to kynurenines (KYN), inducing T-cell suppression either directly or by altering antigen-presenting-cell function. Cyclooxygenase (COX)-2, the rate-limiting enzyme in the synthesis of prostaglandins, is over-expressed by several tumours. We aimed at determining whether COX-2 inhibitors down-regulate the IFN--induced expression of ID...

Recently a bound on negative energy densities in four-dimensional Minkowski spacetime was derived for a minimally coupled, quantized, massless, scalar field in an arbitrary quantum state. The bound has the form of an uncertainty principle-type constraint on the magnitude and duration of the negative energy density seen by a timelike geodesic observer. When spacetime is curved and/or has boundar...