640 research outputs found
Classification and stability of simple homoclinic cycles in R^5
The paper presents a complete study of simple homoclinic cycles in R^5. We
find all symmetry groups Gamma such that a Gamma-equivariant dynamical system
in R^5 can possess a simple homoclinic cycle. We introduce a classification of
simple homoclinic cycles in R^n based on the action of the system symmetry
group. For systems in R^5, we list all classes of simple homoclinic cycles. For
each class, we derive necessary and sufficient conditions for asymptotic
stability and fragmentary asymptotic stability in terms of eigenvalues of
linearisation near the steady state involved in the cycle. For any action of
the groups Gamma which can give rise to a simple homoclinic cycle, we list
classes to which the respective homoclinic cycles belong, thus determining
conditions for asymptotic stability of these cycles.Comment: 34 pp., 4 tables, 30 references. Submitted to Nonlinearit
Chiral gravity in higher dimensions
We construct a chiral theory of gravity in 7 and 8 dimensions, which are
equivalent to Einstein-Cartan theory using less variables. In these dimensions,
we can construct such higher dimensional chiral gravity because of the
existence of gravitational instanton. The octonionic-valued variables in the
theory represent the deviation from the gravitational instanton, and from their
non-associativity, prevents the theory to be SO(n) gauge invariant. Still the
chiral gravity holds G_2 (7-D), and Spin(7) (8-D) gauge symmetry.Comment: 18 pages, no figures. Minor typos corrected. Updated reference
Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution
Recent ground networks and satellite remote-sensing observations have
provided useful data related to spatial and vertical distributions of
mineral dust particles in the atmosphere. However, measurements of temporal
variations and spatial distributions of mineral dust deposition fluxes are
limited in terms of their duration, location, and processes of deposition.
To ascertain temporal variations and spatial distributions of mineral dust
deposition using wet and dry processes, weekly deposition samples were
obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo
(Okinawa) in Japan during October 2008–December 2010 using automatic wet
and dry separating samplers. Mineral dust weights in water-insoluble residue
were estimated from Fe contents measured using an X-ray fluorescence
analyser. Wet and dry deposition fluxes of mineral dusts were both high in
spring and low in summer, showing similar seasonal variations to frequency
of aeolian dust events (Kosa) in Japan. For wet deposition, highest and lowest
annual dust fluxes were found at Toyama (9.6 g m<sup>−2</sup> yr<sup>−1</sup>) and at
Cape Hedo (1.7 g m<sup>−2</sup> yr<sup>−1</sup>) as average values in 2009 and 2010.
Higher wet deposition fluxes were observed at Toyama and Tottori, where
frequent precipitation (> 60% days per month) was observed
during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and
Cape Hedo, the highest and lowest annual dust fluxes were found respectively
at Fukuoka (5.2 g m<sup>−2</sup> yr<sup>−1</sup>) and at
Cape Hedo (2.0 g m<sup>−2</sup> yr<sup>−1</sup>)
as average values in 2009 and 2010. The average ratio of wet and
dry deposition fluxes was the highest at Toyama (3.3) and the lowest at Hedo
(0.82), showing a larger contribution of the dry process at western sites,
probably because of the distance from desert source regions and because of
the effectiveness of the wet process in the dusty season.
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Size distributions of refractory dust particles were obtained using
four-stage filtration: > 20, > 10, > 5, and > 1 μm diameter. Weight fractions of the sum of
> 20 μm and 10–20 μm (giant fraction) were
higher than 50% for most of the event samples. Irrespective of the
deposition type, the giant dust fractions generally decreased with increasing
distance from the source area, suggesting the selective depletion of larger
giant particles during atmospheric transport. Based on temporal variations of
PM<sub>c</sub> (2.5 < <i>D</i> < 10 μm),
ground-based lidar, backward air trajectories, and vertical profiles of
potential temperatures, transport processes of dust particles are discussed
for events with high-deposition and low-deposition flux with high
PM<sub>c</sub>. Low dry dust depositions with high PM<sub>c</sub>
concentrations were observed under stronger (5 K km<sup>−1</sup>) stratification
of potential temperature with thinner and lower (< 2 km)
dust distributions because the PM<sub>c</sub> fraction of dust particles
only survived after depletion of giant dust particles by rapid gravitational
settling at the time they reach Japan. In contrast, transport through a
thicker (> 2 km) dust layer with weak vertical gradient of
potential temperature carry more giant dust particles to Japan. Because giant
dust particles are an important mass fraction of dust accumulation,
especially in the North Pacific, which is known as a high-nutrient,
low-chlorophyll (HNLC) region, the transport height and fraction of giant
dust particles are important factors for studying dust budgets in the
atmosphere and their role in biogeochemical cycles
Thermal and magnetic properties of regenerator material Gd2O2S
金沢大学理工研究域数物科学系Magnetic materials play a significant role in improvement of regenerative cryocooler performance, because they have high volumetric specific heat at magnetic transition temperatures. Gadolinium oxysulfide (Gd2O2S, GOS) that has an antiferromagnetic transition at 5 K improved the cooling performance of cryocoolers when it was used in colder side of the second stage regenerator operating below 10 K. Small magnetic susceptibility and specific heat insensitive to magnetic field is important in order to reduce influence of magnetic field on the performance of cryocooler. We measured magnetization and specific heat of ceramic GOS in magnetic field up to 5 T. The magnetization of GOS represented typical temperature dependence for antiferromagnetic materials and no metamagnetic transition was observed. As for specific heat of GOS, peak temperature decreased from 5.5 to 5.0 K with increasing magnetic field from 0 to 5 T and the transitions remained sharp in magnetic fields. Thermal conductivity of GOS was observed to have very small magnetic field dependence. © Published under licence by IOP Publishing Ltd
Gerstmann-Straussler-Scheinker disease in an Alsatian family: clinical and genetic studies
The clinical progression of Gerstmann-Straussler-Scheinker disease in a family of Alsatian origin is reported. The age of onset and the duration of evolution were variable. The clinical picture became more complex over the generations: in the first generations, isolated dementia and in later generations a triad of pyramidal, pseudobulbar syndromes and dementia associated with spinal cord and cerebellar features. Prion gene analysis showed that four surviving patients carry double missense changes at codons 117 and 129, identical to those found in one case at necropsy and 10 other healthy members of the family. The missense changes were not found in 100 controls. No member of the family had modification of condons 102, 178, or 200. The lod score suggests linkage between the missense change at codon 117 and Gerstmann- Straussler-Scheinker disease in this family
Templated Synthesis of Peptide Nucleic Acids via Sequence-Selective Base-Filling Reactions
The templated synthesis of nucleic acids has previously been achieved through the backbone ligation of preformed nucleotide monomers or oligomers. In contrast, here we demonstrate templated nucleic acid synthesis using a base-filling approach in which individual bases are added to abasic sites of a peptide nucleic acid (PNA). Because nucleobase substrates in this approach are not self-reactive, a base-filling approach may reduce the formation of nontemplated reaction products. Using either reductive amination or amine acylation chemistries, we observed efficient and selective addition of each of the four nucleobases to an abasic site in the middle of the PNA strand. We also describe the addition of single nucleobases to the end of a PNA strand through base filling, as well as the tandem addition of two bases to the middle of the PNA strand. These findings represent an experimental foundation for nonenzymatic information transfer through base filling.Chemistry and Chemical Biolog
Tunicate cytostatic factor TC14-3 induces a polycomb group gene and histone modification through Ca2+ binding and protein dimerization
<p>Abstract</p> <p>Background</p> <p>As many invertebrate species have multipotent cells that undergo cell growth and differentiation during regeneration and budding, many unique and interesting homeostatic factors are expected to exist in those animals. However, our understanding of such factors and global mechanisms remains very poor. Single zooids of the tunicate, <it>Polyandrocarpa </it><it>misakiensis</it>, can give off as many as 40 buds during the life span. Bud development proceeds by means of transdifferentiation of very limited number of cells and tissues. TC14-3 is one of several different but closely related polypeptides isolated from <it>P. misakiensis</it>. It acts as a cytostatic factor that regulates proliferation, adhesion, and differentiation of multipotent cells, although the molecular mechanism remains uncertain. The Polycomb group (PcG) genes are involved in epigenetic control of genomic activity in mammals. In invertebrates except <it>Drosophila</it>, PcG and histone methylation have not been studied so extensively, and genome-wide gene regulation is poorly understood.</p> <p>Results</p> <p>When Phe<sup>65 </sup>of TC14-3 was mutated to an acidic amino acid, the resultant mutant protein failed to dimerize. The replacement of Thr<sup>69 </sup>with Arg<sup>69 </sup>made dimers unstable. When Glu<sup>106 </sup>was changed to Gly<sup>106</sup>, the resultant mutant protein completely lost Ca<sup>2+ </sup>binding. All these mutant proteins lacked cytostatic activity, indicating the requirement of protein dimerization and calcium for the activity. <it>Polyandrocarpa </it><it>Eed</it>, a component of PcG, is highly expressed during budding, like TC14-3. When wild-type and mutant TC14-3s were applied in vivo and in vitro to <it>Polyandrocarpa </it>cells, only wild-type TC14-3 could induce <it>Eed </it>without affecting histone methyltransferase gene expression. Eed-expressing cells underwent trimethylation of histone H3 lysine27. <it>PmEed </it>knockdown by RNA interference rescued cultured cells from the growth-inhibitory effects of TC14-3.</p> <p>Conclusion</p> <p>These results show that in <it>P. misakiensis</it>, the cytostatic activity of TC14-3 is mediated by <it>PmEed </it>and resultant histone modification, and that the gene expression requires both the protein dimerization and Ca<sup>2+</sup>-binding of TC14-3. This system consisting of a humoral factor, PcG, and histone methylation would contribute to the homeostatic regulation of cell growth and terminal differentiation of invertebrate multipotent cells.</p
A direct physical interaction between Nanog and Sox2 regulates embryonic stem cell self-renewal
Embryonic stem (ES) cell self-renewal efficiency is determined by the Nanog protein level. However, the protein partners of Nanog that function to direct self-renewal are unclear. Here, we identify a Nanog interactome of over 130 proteins including transcription factors, chromatin modifying complexes, phosphorylation and ubiquitination enzymes, basal transcriptional machinery members, and RNA processing factors. Sox2 was identified as a robust interacting partner of Nanog. The purified Nanog–Sox2 complex identified a DNA recognition sequence present in multiple overlapping Nanog/Sox2 ChIP-Seq data sets. The Nanog tryptophan repeat region is necessary and sufficient for interaction with Sox2, with tryptophan residues required. In Sox2, tyrosine to alanine mutations within a triple-repeat motif (S X T/S Y) abrogates the Nanog–Sox2 interaction, alters expression of genes associated with the Nanog-Sox2 cognate sequence, and reduces the ability of Sox2 to rescue ES cell differentiation induced by endogenous Sox2 deletion. Substitution of the tyrosines with phenylalanine rescues both the Sox2–Nanog interaction and efficient self-renewal. These results suggest that aromatic stacking of Nanog tryptophans and Sox2 tyrosines mediates an interaction central to ES cell self-renewal
Intermittency analysis of high-lift airfoil with slat cove fillers
Experimental measurements were carried out to assess the aeroacoustic characteristics of 30P30N airfoil fitted with two different types of slat cove fillers at the aeroacoustic facility at the University of Bristol. The results are presented for the angle of attack α = 18◦ at a free-stream velocity of U∞ = 30 m/s which corresponds to a chord-based Reynolds number of Rec = 7 × 10◦ . Simultaneous measurements of the unsteady surface pressure were made at several locations in the vicinity of slat cove and at the far-field location to gain a deeper understanding of the slat noise generation mechanism. The results are analyzed using a higher-order statistical approach to determine the nature of the broadband hump seen at low-frequency for the 30P30N high-lift airfoil observed in recent studies and also to further understand the tone generation mechanism within the slat cavity. A series of cross-correlation and coherence of the unsteady pressure measurements are carried out to identify and isolate the low-frequency hump. Wavelet analysis is performed to investigate the nature of the slat-wing resonant intermittent events in both time and frequency domains. The far-field noise measurement results showed that significant noise reduction can be achieved by the use of slat cove fillers. A series of far-field and near-field correlation are also presented to show the propagated noise from the slat.5s
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