Fictitious fluxes in doped antiferromagnets

In a tight binding model of charged spin-1/2 electrons on a square lattice, a fully polarized ferromagnetic spin configuration generates an apparent U(1) flux given by $2\pi$ times the skyrmion charge density of the ferromagnetic order parameter. We show here that for an antiferromagnet, there are two ``fictitious'' magnetic fields, one staggered and one unstaggered. The staggered topological flux per unit cell can be varied between $-\pi\le\Phi\le\pi$ with a negligible change in the value of the effective nearest neighbor coupling constant whereas the magnitude of the unstaggered flux is strongly coupled to the magnitude of the second neighbor effective coupling.Comment: RevTeX, 5 pages including 4 figure

On the requirements to establish a European radiological preparedness for malicious airborne dispersion scenarios

European computerised decision support systems are currently targeted for large accidental atmospheric contaminant releases from nuclear installations. To make these systems applicable also for malicious dispersion events, such as ‘dirty bomb’ blasts, a series of modifications and extensions are necessary. Also European decision support handbooks need supplementary sections to cover the features of these types of scenarios. An overview is given of the requirements

Genetic variation and trait associations of yield, protein and grain micronutrients for identification of promising sorghum varieties

Sorghum is, globally, the fifth most important cereal after maize, rice, wheat and barley. The crop is tolerant to semi-arid and arid climatic conditions. Twenty-five sorghum varieties grown in South Africa were evaluated in the field at two locations with the objective of identifying high yielding, micronutrient dense genotypes. Two clusters were formed based on measured traits. Tx430 (G13), CIMMYT entry 49 (G12), E35-1 (G16), Framida (G19), IS1934 (G7) and IS14380 (G14) formed cluster A. The rest of the sorghum entries formed cluster B. Wide variation was exhibited for grain yield, ranging from 1.12 t ha−1 to 3.96 t ha−1 with a mean grain yield of 2.83 tha−1. Analysis of variance also revealed significant differences among the varieties for protein, total starch, amylose and mineral content. Two varieties, Tx430 and AR-3048 exhibited very high protein content. Fe content ranged from 43.7 mg kg−1 (Kuyuma) to 61.2 mg kg−1 (IS14380) with an average of 50.5 mg kg−1. Zn content ranged from 13.7 mg kg−1 (Macia) to 23.4 mg kg−1 (Tx430) with a mean of 17.4 mg kg−1. Grain yield was significantly positively correlated with plant height, panicle weight and thousand kernel weight. Significant positive correlations were observed between Fe content and Zn, Cu, Mn and P. This data indicated that simultaneous genetic improvement of sorghum varieties for Fe and other important minerals, and starch content in the same genetic background was possible, without a penalty to grain yield

Operational sex ratio, sexual conflict and the intensity of sexual selection.

Modern sexual selection theory indicates that reproductive costs rather than the operational sex ratio predict the intensity of sexual selection. We investigated sexual selection in the polygynandrous common lizard Lacerta vivipara. This species shows male aggression, causing high mating costs for females when adult sex ratios (ASR) are male-biased. We manipulated ASR in 12 experimental populations and quantified the intensity of sexual selection based on the relationship between reproductive success and body size. In sharp contrast to classical sexual selection theory predictions, positive directional sexual selection on male size was stronger and positive directional selection on female size weaker in female-biased populations than in male-biased populations. Thus, consistent with modern theory, directional sexual selection on male size was weaker in populations with higher female mating costs. This suggests that the costs of breeding, but not the operational sex ratio, correctly predicted the strength of sexual selection

Faster Approximate String Matching for Short Patterns

We study the classical approximate string matching problem, that is, given strings $P$ and $Q$ and an error threshold $k$, find all ending positions of substrings of $Q$ whose edit distance to $P$ is at most $k$. Let $P$ and $Q$ have lengths $m$ and $n$, respectively. On a standard unit-cost word RAM with word size $w \geq \log n$ we present an algorithm using time $$O(nk \cdot \min(\frac{\log^2 m}{\log n},\frac{\log^2 m\log w}{w}) + n)$$ When $P$ is short, namely, $m = 2^{o(\sqrt{\log n})}$ or $m = 2^{o(\sqrt{w/\log w})}$ this improves the previously best known time bounds for the problem. The result is achieved using a novel implementation of the Landau-Vishkin algorithm based on tabulation and word-level parallelism.Comment: To appear in Theory of Computing System

Can sexual selection drive female life histories? A comparative study on Galliform birds

Sexual selection is an important driver of many of the most spectacular morphological traits that we find in the animal kingdom (for example see Andersson, 1994). As such, sexual selection is most often emphasized as

Benthic marine calcifiers coexist with CaCO3-undersaturated seawater worldwide

Ocean acidification and decreasing seawater saturation state with respect to calcium carbonate (CaCO3) minerals have raised concerns about the consequences to marine organisms, especially those building structures made of CaCO3. A large proportion of benthic marine calcifiers incorporate Mg2+ into their calcareous structures (i.e., Mg-calcite) which, in general, reduces mineral stability. The vulnerability of some marine calcifiers to ocean acidification is related to the solubility of their calcareous structures, but not all marine organisms conform to this because of sophisticated biological and physiological mechanisms to construct and maintain CaCO3 structures. Few studies have considered seawater saturation state with respect to species-specific mineralogy in evaluating the effect of ocean acidification on marine organisms. Here, a global dataset of skeletal mol % MgCO3 of benthic calcifiers and in situ environmental conditions (temperature, salinity, pressure, and [CO32-]) spanning a depth range of 0 m (subtidal/neritic) to 5500 m (abyssal) was assembled to calculate in situ seawater saturation states with respect to species-specific Mg-calcite mineral compositions (?Mg-x). Up to 20% of all studied calcifiers at depths <1200 m and approximately 90% of calcifiers at depths >1200 m currently experience seawater mineral undersaturation with respect to their skeletal mineral phase (?Mg-x<1). We conclude that as a result of predicted anthropogenic ocean acidification over the next 150 years, the predicted decrease in seawater mineral saturation, will expose approximately 50% (<1200 m) and 100% (>1200 m) of all studied calcifying species to seawater undersaturation. These observations underscore concerns over the ability of marine benthic calcifiers to continue to construct and maintain their calcareous structures under these conditions. We advocate that ocean acidification tipping points can only be understood by assessing species-specific responses, and because of different seawater ?Mg-x present in all marine ecosystems

Simultaneous age-dependent and age-independent sexual selection in the lekking black grouse (Lyrurus tetrix)

1. Individuals' reproductive success is often strongly associated with their 18 age, with typical patterns of early life reproductive improvement and late 19 life senescence. These age-related patterns are due to the inherent trade-20 offs between life history traits competing for a limited amount of resources 21 available to the organisms. In males, such trade-offs are exacerbated by the 22 resource requirements associated with the expression of costly sexual 23 2 traits, leading to dynamic changes in trait expression throughout their 24 lifespan. 25 2. Due to the age-dependency of male phenotypes, the relationship between 26 the expression of male traits and mating success can also vary with male 27 age. Hence, using longitudinal data in a lekking species with strong sexual 28 selection – the black grouse Lyrurus tetrix – we quantified the effects of 29 age, lifespan and age of first lek attendance (AFL) on male annual mating 30 success (AMS) to separate the effects of within-individual improvement 31 and senescence on AMS from selective (dis)appearance of certain 32 phenotypes. Then, we used male AMS to quantify univariate and 33 multivariate sexual selection gradients on male morphological and 34 behavioural traits with and without accounting for age and age-related 35 effects of other traits. 36 3. Male AMS increased with age and there was no significant reproductive 37 senescence. Most males never copulated and of the ones that did, the 38 majority had only one successful year. Lifespan was unrelated to AMS, but 39 early AFL tended to lead to higher AMS at ages 1 to 3. AMS was related 40 to morphological and behavioural traits when male age was ignored. 41 Accounting for age and age-specific trait effects (i.e. the interaction 42 between a trait and age) reduced the magnitude of the selection gradients 43 and revealed that behavioural traits are under consistent sexual selection, 44 while sexual selection on morphological traits is stronger in old males. 45 4. Therefore, sexual selection in black grouse operates primarily on male 46 behaviour and morphological traits may act as additional cues to 47 supplement female choice. These results demonstrate the multifaceted 48 3 influence of age on both fitness and sexual traits and highlight the 49 importance of accounting for such effects when quantifying sexual 50 selection

Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays

Bose-Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in the four-momentum difference range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be smaller than that of charged pions. This result is in qualitative agreement with the string fragmentation model