Sampling the progression of domain-initial denasalization in Seoul Korean

Word-initial nasals in Korean are known to exhibit prosody-sensitive denasalization. The literature on the subject is still scarce and even the basic description of the process is debated. This study tested the speculation that inconsistencies in the literature may be explained if certain features of denasalization have developed relatively recently as part of an ongoing sound change. Based on apparent-time data from thirty-two speakers of Seoul Korean, the study explored the development of denasalization over a fifty-year period. The phonetic manifestations of domain-initial nasals were examined, along with the effects of prosodic position, place of articulation, and the height of the following vowel. The results revealed that denasalization has advanced rapidly over time, acquiring more plosive-like features of devoicing as well as a complete lack of nasality. Alveolar nasals before a high vowel were most likely to show denasalization and devoicing. Interestingly, the cumulative effect of prosody became weakest and partial denasalization was least likely for the younger group. Based on these results, we speculate that Korean denasalization is in the process of being stabilized into a discrete phrase-level process from a more general, gradient phenomenon of domain-initial strengthening, consistent with the theory of the life cycle of phonological processes. Keywords: denasalization; domain-initial strengthening; articulatory strengthening; fortition; Korean; sound change; rule scattering; life cycle of phonological processes; apparent tim

Assessing the Effects of Road Pricing on an Industry: The Grain Handling and Transportation System in Saskatchewan

This research evaluates the merits of road pricing scenarios affecting a single industry almost exclusively – grain movement on the rural road network in the west central region of the Canadian province of Saskatchewan. Policies in the Canadian grain handling and transportation industry have led to increased use of rural roads, accelerating road deterioration in the region. Using a simulated optimization framework to compare road pricing schemes, we find that a policy of differential road pricing based on known road maintenance costs generates the lowest total social costs. The differences between the simulated social costs in the pricing scenarios are surprisingly small

A CRISPR-Cas9 sex-ratio distortion system for genetic control.

Genetic control aims to reduce the ability of insect pest populations to cause harm via the release of modified insects. One strategy is to bias the reproductive sex ratio towards males so that a population decreases in size or is eliminated altogether due to a lack of females. We have shown previously that sex ratio distortion can be generated synthetically in the main human malaria vector Anopheles gambiae, by selectively destroying the X-chromosome during spermatogenesis, through the activity of a naturally-occurring endonuclease that targets a repetitive rDNA sequence highly-conserved in a wide range of organisms. Here we describe a CRISPR-Cas9 sex distortion system that targets ribosomal sequences restricted to the member species of the Anopheles gambiae complex. Expression of Cas9 during spermatogenesis resulted in RNA-guided shredding of the X-chromosome during male meiosis and produced extreme male bias among progeny in the absence of any significant reduction in fertility. The flexibility of CRISPR-Cas9 combined with the availability of genomic data for a range of insects renders this strategy broadly applicable for the species-specific control of any pest or vector species with an XY sex-determination system by targeting sequences exclusive to the female sex chromosome

Prevalence of the vanB2 gene cluster in VanB glycopeptide-resistant enterococci in the United Kingdom and the Republic of Ireland and its association with a Tn5382-like element

A total of 204 vanB enterococcal isolates, isolated between 1989 and 1999 from patients in 59 different hospitals in England, Wales, and Scotland and from a single hospital in the Republic of Ireland, were examined. Nucleotide sequencing and HhaI digestion of a fragment of the vanB gene was used to distinguish between the vanB1, vanB2, andvanB3 gene clusters (7). Based on theirvanB-HhaI restriction fragment length polymorphism (RFLP) profiles, 202 (99%) isolates contained vanB2. The presence of vanB1 in two isolates was confirmed by sequence analysis

On isotropic cylindrically symmetric stellar models

We attempt to match the most general cylindrically symmetric vacuum space-time with a Robertson-Walker interior. The matching conditions show that the interior must be dust filled and that the boundary must be comoving. Further, we show that the vacuum region must be polarized. Imposing the condition that there are no trapped cylinders on an initial time slice, we can apply a result of Thorne's and show that trapped cylinders never evolve. This results in a simplified line element which we prove to be incompatible with the dust interior. This result demonstrates the impossibility of the existence of an isotropic cylindrically symmetric star (or even a star which has a cylindrically symmetric portion). We investigate the problem from a different perspective by looking at the expansion scalars of invariant null geodesic congruences and, applying to the cylindrical case, the result that the product of the signs of the expansion scalars must be continuous across the boundary. The result may also be understood in relation to recent results about the impossibility of the static axially symmetric analogue of the Einstein-Straus model.Comment: 13 pages. To appear in Classical and Quantum Gravit

Solving the time-dependent Schr\"odinger equation with absorbing boundary conditions and source terms in Mathematica 6.0

In recent decades a lot of research has been done on the numerical solution of the time-dependent Schr\"odinger equation. On the one hand, some of the proposed numerical methods do not need any kind of matrix inversion, but source terms cannot be easily implemented into this schemes; on the other, some methods involving matrix inversion can implement source terms in a natural way, but are not easy to implement into some computational software programs widely used by non-experts in programming (e.g. Mathematica). We present a simple method to solve the time-dependent Schr\"odinger equation by using a standard Crank-Nicholson method together with a Cayley's form for the finite-difference representation of evolution operator. Here, such standard numerical scheme has been simplified by inverting analytically the matrix of the evolution operator in position representation. The analytical inversion of the N x N matrix let us easily and fully implement the numerical method, with or without source terms, into Mathematica or even into any numerical computing language or computational software used for scientific computing.Comment: 15 pages, 7 figure

A Characterisation of Strong Wave Tails in Curved Space-Times

A characterisation of when wave tails are strong is proposed. The existence of a curvature induced tail (i.e. a Green's function term whose support includes the interior of the light-cone) is commonly understood to cause backscattering of the field governed by the relevant wave equation. Strong tails are characterised as those for which the purely radiative part of the field is backscattered. With this definition, it is shown that electromagnetic waves in asymptotically flat space-times and fields governed by tail-free propagation have weak tails, but minimally coupled scalar fields in a cosmological scenario have strong tails.Comment: 17 pages, Revtex, to appear in Classical and Quantum Gravit

Social networks and labour productivity in Europe: An empirical investigation

This paper uses firm-level data recorded in the AMADEUS database to investigate the distribution of labour productivity in different European countries. We find that the upper tail of the empirical productivity distributions follows a decaying power-law, whose exponent $\alpha$ is obtained by a semi-parametric estimation technique recently developed by Clementi et al. (2006). The emergence of "fat tails" in productivity distribution has already been detected in Di Matteo et al. (2005) and explained by means of a model of social network. Here we show that this model is tested on a broader sample of countries having different patterns of social network structure. These different social attitudes, measured using a social capital indicator, reflect in the power-law exponent estimates, verifying in this way the existence of linkages among firms' productivity performance and social network.Comment: LaTeX2e; 18 pages with 3 figures; Journal of Economic Interaction and Coordination, in pres