Optimization of Magnetooptic Device by Low Switching Field Domains

This paper expounds on the optimization of magnetooptic devices using preferential domains that switch at low field strengths. In particular, an all-optical switch for transparent networks based on theMach-Zehnder interferometer configuration is examined in detail. The switch utilizes bismuth-substituted iron garnets with a specific composition of (Bi1.1Tb1.9)(Fe4.25Ga0.75)O12 as Faraday rotators. It is proposed that switch figures of merit can be improved by preferentially choosing domains which align with applied fields at field strengths much lower than required by the bulk material. Measurement of magnetic domain orientation in the material and Faraday rotation within domains is reported. The domain behavior in low magnetic fields is also investigated to achieve a switch with lower switching times and higher extinction ratios

THE EFFECT OF EXCHANGE RATE VOLATILITY ON WHEAT TRADE WORLDWIDE

A modified gravity-type model was employed to evaluate the effect of exchange rate volatility on wheat exports worldwide. Special attention was given to the econometric properties of the gravity model within panel framework. Short and long-term measures of exchange rate volatility were constructed and compared. Both measures of exchange rate volatility have exhibited a negative effect on world wheat trade and the long-term effect was even larger. This result implies that exchange rate volatility is an important factor in explaining the trade pattern of wheat trade worldwide. Keywords: wheat, export, exchange rate, volatility, gravity model, and panel data.wheat, export, exchange rate, volatility, gravity model, and panel data., International Relations/Trade,

THE EFFECT OF EXCHANGE RATE VOLATILITY ON WHEAT TRADE WORLDWIDE

A modified gravity-type model was employed to evaluate the effect of exchange rate volatility on wheat exports worldwide. Special attention was given to the econometric properties of the gravity model within a panel framework. Short and long-term measures of exchange rate volatility were constructed and compared. Both measures of exchange rate volatility exhibited negative effects on world wheat trade, with even greater effects in the long-term measure. This result implies that exchange rate volatility is an important factor in explaining the trade pattern of wheat worldwide.wheat, export, exchange rate, volatility, gravity model, and panel data., International Relations/Trade,

Approximation Algorithms and Hardness for nn-Pairs Shortest Paths and All-Nodes Shortest Cycles

We study the approximability of two related problems on graphs with $n$ nodes and $m$ edges: $n$-Pairs Shortest Paths ($n$-PSP), where the goal is to find a shortest path between $O(n)$ prespecified pairs, and All Node Shortest Cycles (ANSC), where the goal is to find the shortest cycle passing through each node. Approximate $n$-PSP has been previously studied, mostly in the context of distance oracles. We ask the question of whether approximate $n$-PSP can be solved faster than by using distance oracles or All Pair Shortest Paths (APSP). ANSC has also been studied previously, but only in terms of exact algorithms, rather than approximation. We provide a thorough study of the approximability of $n$-PSP and ANSC, providing a wide array of algorithms and conditional lower bounds that trade off between running time and approximation ratio. A highlight of our conditional lower bounds results is that for any integer $k\ge 1$, under the combinatorial $4k$-clique hypothesis, there is no combinatorial algorithm for unweighted undirected $n$-PSP with approximation ratio better than $1+1/k$ that runs in $O(m^{2-2/(k+1)}n^{1/(k+1)-\epsilon})$ time. This nearly matches an upper bound implied by the result of Agarwal (2014). A highlight of our algorithmic results is that one can solve both $n$-PSP and ANSC in $\tilde O(m+ n^{3/2+\epsilon})$ time with approximation factor $2+\epsilon$ (and additive error that is function of $\epsilon$), for any constant $\epsilon>0$. For $n$-PSP, our conditional lower bounds imply that this approximation ratio is nearly optimal for any subquadratic-time combinatorial algorithm. We further extend these algorithms for $n$-PSP and ANSC to obtain a time/accuracy trade-off that includes near-linear time algorithms.Comment: Abstract truncated to meet arXiv requirement. To appear in FOCS 202

Improved formulation for Faraday rotation characterization

The analysis of complex structures consisting of fibers, films, birefringent, and magnetic materials is greatly aided by the availability of an analysis structure. Jones calculus is typically utilized in the course of such analyses. However, standard Jones calculus does not account for the effect of reflections. An improved formulation for the characterization of Faraday rotation that alleviates this shortcoming is reported here and is integral for the proper analysis of devices employing magneto-optic effects

Cross-country comparison of parental reports and objective measures of sleep patterns of typically developing children and autistic children between the UK and South Korea

Sleep duration and disturbances in typically developing (TD) children have been found to vary across countries. Given the impact of culture on sleep patterns in TD children, it is also necessary to examine the impact of culture on sleep patterns in children with atypical development. However, previous studies have often relied only on parent reports of children's sleep. Hence, the present study conducted a cross-cultural comparison of sleep duration and disturbances of school-aged TD children and autistic children in the UK and South Korea (hereafter Korea) using both subjective and objective sleep measurements. Cultural differences were observed in both actigraphy measures and parent reports of children's sleep duration and disturbances. Both TD children and autistic children in Korea had a later bedtime, later getting up time and shorter nocturnal sleep duration than their peers in the UK (p < .05). Furthermore, greater parent-reported sleep disturbances were reported in TD children in Korea compared to TD children in the UK and in autistic children in the UK compared to autistic children in Korea. Correlational analyses indicated that most parent-reported measures of children's sleep did not significantly correlate with objective measures and child reports, suggesting that studies on children's sleep can benefit by collecting data from multiple sources. Taken together, these findings suggest a cultural influence on sleep duration and disturbances of both TD children and autistic children. This study raises questions for further research to identify factors underlying cultural differences in children's sleep duration and disturbances

Maternal fucosyltransferase 2 status affects the gut bifidobacterial communities of breastfed infants.

BackgroundIndividuals with inactive alleles of the fucosyltransferase 2 gene (FUT2; termed the 'secretor' gene) are common in many populations. Some members of the genus Bifidobacterium, common infant gut commensals, are known to consume 2'-fucosylated glycans found in the breast milk of secretor mothers. We investigated the effects of maternal secretor status on the developing infant microbiota with a special emphasis on bifidobacterial species abundance.ResultsOn average, bifidobacteria were established earlier and more often in infants fed by secretor mothers than in infants fed by non-secretor mothers. In secretor-fed infants, the relative abundance of the Bifidobacterium longum group was most strongly correlated with high percentages of the order Bifidobacteriales. Conversely, in non-secretor-fed infants, Bifidobacterium breve was positively correlated with Bifidobacteriales, while the B. longum group was negatively correlated. A higher percentage of bifidobacteria isolated from secretor-fed infants consumed 2'-fucosyllactose. Infant feces with high levels of bifidobacteria had lower milk oligosaccharide levels in the feces and higher amounts of lactate. Furthermore, feces containing different bifidobacterial species possessed differing amounts of oligosaccharides, suggesting differential consumption in situ.ConclusionsInfants fed by non-secretor mothers are delayed in the establishment of a bifidobacteria-laden microbiota. This delay may be due to difficulties in the infant acquiring a species of bifidobacteria able to consume the specific milk oligosaccharides delivered by the mother. This work provides mechanistic insight into how milk glycans enrich specific beneficial bacterial populations in infants and reveals clues for enhancing enrichment of bifidobacterial populations in at risk populations - such as premature infants

The first generation of a BAC-based physical map of Brassica rapa

<p>Abstract</p> <p>Background</p> <p>The genus <it>Brassica </it>includes the most extensively cultivated vegetable crops worldwide. Investigation of the <it>Brassica </it>genome presents excellent challenges to study plant genome evolution and divergence of gene function associated with polyploidy and genome hybridization. A physical map of the <it>B. rapa </it>genome is a fundamental tool for analysis of <it>Brassica </it>"A" genome structure. Integration of a physical map with an existing genetic map by linking genetic markers and BAC clones in the sequencing pipeline provides a crucial resource for the ongoing genome sequencing effort and assembly of whole genome sequences.</p> <p>Results</p> <p>A genome-wide physical map of the <it>B. rapa </it>genome was constructed by the capillary electrophoresis-based fingerprinting of 67,468 Bacterial Artificial Chromosome (BAC) clones using the five restriction enzyme SNaPshot technique. The clones were assembled into contigs by means of FPC v8.5.3. After contig validation and manual editing, the resulting contig assembly consists of 1,428 contigs and is estimated to span 717 Mb in physical length. This map provides 242 anchored contigs on 10 linkage groups to be served as seed points from which to continue bidirectional chromosome extension for genome sequencing.</p> <p>Conclusion</p> <p>The map reported here is the first physical map for <it>Brassica </it>"A" genome based on the High Information Content Fingerprinting (HICF) technique. This physical map will serve as a fundamental genomic resource for accelerating genome sequencing, assembly of BAC sequences, and comparative genomics between <it>Brassica </it>genomes. The current build of the <it>B. rapa </it>physical map is available at the <it>B. rapa </it>Genome Project website for the user community.</p

Genome-wide comparative analysis of the Brassica rapa gene space reveals genome shrinkage and differential loss of duplicated genes after whole genome triplication

Euchromatic regions of the Brassica rapa genome were sequenced and mapped onto the corresponding regions in the Arabidopsis thaliana genome