COHEN-MACAULAY MODULES AND HOLONOMIC MODULES OVER FILTERED RINGS

We study Gorenstein dimension and grade of a module M over a filtered ring whose associated graded ring is a commutative Noetherian ring. An equality or an inequality between these invariants of a filtered module and its associated graded module is the most valuable property for an investigation of filtered rings. We prove an inequality G-dimM <= G-dim grM and an equality grade M = grade grM, whenever Gorenstein dimension of grM is finite (Theorems 2.3 and 2.8). We would say that the use of G-dimension adds a new viewpoint for studying filtered rings and modules. We apply these results to a filtered ring with a Cohen-Macaulay or Gorenstein associated graded ring and study a Cohen-Macaulay, perfect, or holonomic module.ArticleCommunications in Algebra. 37(2):406-430 (2009)journal articl

The extinct tree fern Tempskya Corda from the Albian of Spain: Palaeophytogeographical and palaeoenvironmental implications

New evidence of the extinct tree fern of the genus Tempskya Corda from Albian deposits in western Eurasia (northeastern Spain) is presented. These plant fossil remains consist of several silicified false trunks measuring up to 1.20m long, some of which still preserve the apex. Rhizomes and petioles are more abundant in the apical zone of the false trunk. Some false trunks preserve charcoalified tissues that can be interpreted as evidence that palaeo-wildfires affected the false trunks several times from mostly the same direction. Sedimentological evidence suggests that the fern habitat was close to coastal, tidally influenced environments. These new fossils from the Albian of Spain fill the chronological and distributional gap of Tempskya that existed in Eurasia during the Early Cretaceous. Temporal and spatial changes in Tempskya distributions are proposed on several palaeogeographical maps

Distribution of Introns in Fungal Histone Genes

Saccharomycotina and Taphrinomycotina lack intron in their histone genes, except for an intron in one of histone H4 genes of Yarrowia lipolytica. On the other hand, Basidiomycota and Perizomycotina have introns in their histone genes. We compared the distributions of 81, 47, 79, and 98 introns in the fungal histone H2A, H2B, H3, and H4 genes, respectively. Based on the multiple alignments of the amino acid sequences of histones, we identified 19, 13, 31, and 22 intron insertion sites in the histone H2A, H2B, H3, and H4 genes, respectively. Surprisingly only one hot spot of introns in the histone H2A gene is shared between Basidiomycota and Perizomycotina, suggesting that most of introns of Basidiomycota and Perizomycotina were acquired independently. Our findings suggest that the common ancestor of Ascomycota and Basidiomycota maybe had a few introns in the histone genes. In the course of fungal evolution, Saccharomycotina and Taphrinomycotina lost the histone introns; Basidiomycota and Perizomycotina acquired other introns independently. In addition, most of the introns have sequence similarity among introns of phylogenetically close species, strongly suggesting that horizontal intron transfer events between phylogenetically distant species have not occurred recently in the fungal histone genes

Megabits secure key rate quantum key distribution

Quantum cryptography (QC) can provide unconditional secure communication between two authorized parties based on the basic principles of quantum mechanics. However, imperfect practical conditions limit its transmission distance and communication speed. Here we implemented the differential phase shift (DPS) quantum key distribution (QKD) with up-conversion assisted hybrid photon detector (HPD) and achieved 1.3 M bits per second secure key rate over a 10-km fiber, which is tolerant against the photon number splitting (PNS) attack, general collective attacks on individual photons, and any other known sequential unambiguous state discrimination (USD) attacks.Comment: 14 pages, 4 figure

Metabolism of Toxic Sugars by Strains of the Bee Gut Symbiont Gilliamella apicola.

Social bees collect carbohydrate-rich food to support their colonies, and yet, certain carbohydrates present in their diet or produced through the breakdown of pollen are toxic to bees. The gut microbiota of social bees is dominated by a few core bacterial species, including the Gram-negative species Gilliamella apicola We isolated 42 strains of G. apicola from guts of honey bees and bumble bees and sequenced their genomes. All of the G. apicola strains share high 16S rRNA gene similarity, but they vary extensively in gene repertoires related to carbohydrate metabolism. Predicted abilities to utilize different sugars were verified experimentally. Some strains can utilize mannose, arabinose, xylose, or rhamnose (monosaccharides that can cause toxicity in bees) as their sole carbon and energy source. All of the G. apicola strains possess a manO-associated mannose family phosphotransferase system; phylogenetic analyses suggest that this was acquired from Firmicutes through horizontal gene transfer. The metabolism of mannose is specifically dependent on the presence of mannose-6-phosphate isomerase (MPI). Neither growth rates nor the utilization of glucose and fructose are affected in the presence of mannose when the gene encoding MPI is absent from the genome, suggesting that mannose is not taken up by G. apicola strains which harbor the phosphotransferase system but do not encode the MPI. Given their ability to simultaneously utilize glucose, fructose, and mannose, as well as the ability of many strains to break down other potentially toxic carbohydrates, G. apicola bacteria may have key roles in improving dietary tolerances and maintaining the health of their bee hosts. Bees are important pollinators of agricultural plants. Our study documents the ability of Gilliamella apicola, a dominant gut bacterium in honey bees and bumble bees, to utilize several sugars that are harmful to bee hosts. Using genome sequencing and growth assays, we found that the ability to metabolize certain toxic carbohydrates is directly correlated with the presence of their respective degradation pathways, indicating that metabolic potential can be accurately predicted from genomic data in these gut symbionts. Strains vary considerably in their range of utilizable carbohydrates, which likely reflects historical horizontal gene transfer and gene deletion events. Unlike their bee hosts, G. apicola bacteria are not detrimentally affected by growth on mannose-containing medium, even in strains that cannot metabolize this sugar. These results suggest that G. apicola may be an important player in modulating nutrition in the bee gut, with ultimate effects on host health