1,141 research outputs found
Ensemble dependence in the Random transverse-field Ising chain
In a disordered system one can either consider a microcanonical ensemble,
where there is a precise constraint on the random variables, or a canonical
ensemble where the variables are chosen according to a distribution without
constraints. We address the question as to whether critical exponents in these
two cases can differ through a detailed study of the random transverse-field
Ising chain. We find that the exponents are the same in both ensembles, though
some critical amplitudes vanish in the microcanonical ensemble for correlations
which span the whole system and are particularly sensitive to the constraint.
This can \textit{appear} as a different exponent. We expect that this apparent
dependence of exponents on ensemble is related to the integrability of the
model, and would not occur in non-integrable models.Comment: 8 pages, 12 figure
The role of lithospheric flexure in the landscape evolution of the Wilkes Subglacial Basin and Transantarctic Mountains, East Antarctica
Reconstructions of the bedrock topography of Antarctica since the Eocene–Oligocene Boundary (ca. 34 Ma) provide important constraints for modelling Antarctic ice sheet evolution. This is particularly important in regions where the bedrock lies below sea level, since in these sectors the overlying ice sheet is thought to be most susceptible to past and future change. Here we use 3D flexural modelling to reconstruct the evolution of the topography of the Wilkes Subglacial Basin (WSB) and Transantarctic Mountains (TAM) in East Antarctica. We estimate the spatial distribution of glacial erosion beneath the East Antarctic Ice Sheet, and restore this material to the topography, which is also adjusted for associated flexural isostatic responses. We independently constrain our post‐34 Ma erosion estimates using offshore sediment stratigraphy interpretations. Our reconstructions provide a better‐defined topographic boundary condition for modelling early East Antarctic Ice Sheet history. We show that the majority of glacial erosion and landscape evolution occurred prior to 14 Ma, which we interpret to reflect more dynamic and erosive early ice sheet behaviour. In addition, we use closely‐spaced 2D flexural models to test previously proposed hypotheses for a flexural origin of the TAM and WSB. The pre‐34 Ma topography shows lateral variations along the length of the TAM and WSB that cannot be explained by uniform flexure along the front of the TAM. We show that some of these variations may be explained by additional flexural uplift along the south‐western flank of the WSB and the Rennick Graben in northern Victoria Land
Recent advance in high manufacturing readiness level and high temperature CMOS mixed-signal integrated circuits on silicon carbide
A high manufacturing readiness level silicon carbide (SiC) CMOS technology is presented. The unique process flow enables the monolithic integration of pMOS and nMOS transistors with passive circuit elements capable of operation at temperatures of 300 °C and beyond. Critical to this functionality is the behaviour of the gate dielectric and data for high temperature capacitance–voltage measurements are reported for SiO2/4H-SiC (n and p type) MOS structures. In addition, a summary of the long term reliability for a range of structures including contact chains to both n-type and p-type SiC, as well as simple logic circuits is presented, showing function after 2000 h at 300 °C. Circuit data is also presented for the performance of digital logic devices, a 4 to 1 analogue multiplexer and a configurable timer operating over a wide temperature range. A high temperature micro-oven system has been utilised to enable the high temperature testing and stressing of units assembled in ceramic dual in line packages, including a high temperature small form-factor SiC based bridge leg power module prototype, operated for over 1000 h at 300 °C. The data presented show that SiC CMOS is a key enabling technology in high temperature integrated circuit design. In particular it provides the ability to realise sensor interface circuits capable of operating above 300 °C, accommodate shifts in key parameters enabling deployment in applications including automotive, aerospace and deep well drilling
Aquabacterium limnoticum sp nov., isolated from a freshwater spring
A Gram-negative, facultatively anaerobic, short-rod-shaped, non-motile and non-spore-forming bacterial strain, designated ABP-4(T), was isolated from a freshwater spring in Taiwan and was characterized using the polyphasic taxonomy approach. Growth occurred at 20-40 degrees C (optimum, 30-37 degrees C), at pH 7.0-10.0 (optimum, pH 7.0-9.0) and with 0-3 % NaCl (optimum, 0 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain ABP-4(T), together with Aquabacterium fontiphilum CS-6(T) (96.4 % sequence similarity), Aquabacterium commune B8(T) (96.1 %), Aquabacterium citratiphilum B4(T) (95.5 %) and Aquabacterium parvum B6(T) (94.7 %), formed a deep line within the order Burkholderiales. Strain ABP-4(T) contained summed feature 3 (comprising C-16:1 omega 7c and/or C-16:1 omega 6c), C-18:1 omega 7c and C-16:0 as predominant fatty acids. The major cellular hydroxy fatty acid was C-10:0 3-OH. The major isoprenoid quinone was Q-8 and the DNA G+C content was 68.6 mol%. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine, diphosphatidylglycerol and several uncharacterized phospholipids. The DNA-DNA relatedness of strain ABP-4(T) with respect to recognized species of the genus Aquabacterium was less than 70 %. On the basis of the genotypic, chemotaxonomic and phenotypic data, strain ABP-4(T) represents a novel species in the genus Aquabacterium, for which the name Aquabacterium limnoticum sp. nov. is proposed. The type strain is ABP-4(T) (=BCRC 80167(T)=KCTC 23306(T))
Operator renewal theory and mixing rates for dynamical systems with infinite measure
We develop a theory of operator renewal sequences in the context of infinite
ergodic theory. For large classes of dynamical systems preserving an infinite
measure, we determine the asymptotic behaviour of iterates of the
transfer operator. This was previously an intractable problem.
Examples of systems covered by our results include (i) parabolic rational
maps of the complex plane and (ii) (not necessarily Markovian) nonuniformly
expanding interval maps with indifferent fixed points.
In addition, we give a particularly simple proof of pointwise dual ergodicity
(asymptotic behaviour of ) for the class of systems under
consideration.
In certain situations, including Pomeau-Manneville intermittency maps, we
obtain higher order expansions for and rates of mixing. Also, we obtain
error estimates in the associated Dynkin-Lamperti arcsine laws.Comment: Preprint, August 2010. Revised August 2011. After publication, a
minor error was pointed out by Kautzsch et al, arXiv:1404.5857. The updated
version includes minor corrections in Sections 10 and 11, and corresponding
modifications of certain statements in Section 1. All main results are
unaffected. In particular, Sections 2-9 are unchanged from the published
versio
Deinococcus ficus sp nov., isolated from the rhizosphere of Ficus religiosa L
A pale-pink strain (CC-FR2-10(T)) from the rhizosphere of the sacred tree Ficus religiosa L. in Taiwan was investigated by using a polyphasic taxonomic approach. The cells were Gram-positive, rod-shaped and non-spore-forming. Phylogenetic analyses using the 16S rRNA gene sequence of the isolate indicated that the organism belongs to the genus Deinococcus, the highest sequence similarities being found with Deinococcus grandis (96.1%), Deinococcus radiodurans (94.3%),Deinococcus radiopugnans (93.2%), Deinococcus indicus (93.0%), Deinococcus proteolyticus (92.5%), Deinococcus murrayi (92.4%) and Deinococcus geothermalis (90.7%). The DNA-DNA relatedness with respect to D. grandis DSM 3963(T) was 17.9%. Chemotaxonomic data revealed that strain CC-FR2-10(T) contains only menaquinone MK-8 as the respiratory quinone, unknown phosphoglycolipids as the predominant polar lipids and 16:1 omega 7c, 17:1 omega 8c and 17:1 omega 9c iso as the predominant fatty acids. The biochemical and chemotaxonomic properties demonstrate that strain CC-FR2-10(T) represents a novel species, for which the name Deinococcus ficus sp. nov. is proposed. The type strain is CC-FR2-10(T) (= CCUG 53391(T) = CIP 108832(T))
Transfer of Flexibacter sancti, Flexibacter filiformis, Flexibacter japonensis and Cytophaga arvensicola to the genus Chitinophaga and description of Chitinophaga skermanii sp nov
Analysis of the 16S rRNA gene sequences of species currently assigned to the genus Flexibacter has shown extensive intrageneric phylogenetic heterogeneity. It has been shown in previous studies that the species [Flexibacter] sancti, [Flexibacter] filiformis and [Flexibacter] japonensis were most closely related to Chitinophaga pinensis. In addition, [Cytophaga] arvensicola and species of the genus Terrimonas also clustered into this phylogenetic group. Although the similarities of 16S rRNA gene sequences were low (88.5-96.4%), there is no evidence for clear phenotypic differences between these organisms that justify assignment to different genera. A proposal is made to transfer these species to the genus Chitinophaga as Chitinophaga sancti comb. nov., Chitinophaga filiformis comb. nov., Chitinophaga japonenis comb. nov. and Chitinophaga arvensicola comb. nov. on the basis of phylogenetic and phenotypic data. Furthermore, a novel species is described within this genus, Chitinophaga skermanii sp. nov., with strain CC-SG1B(T) (=CCUG 52510(T)=CIP 109140(T)) as the type strain
Quantum Griffiths effects and smeared phase transitions in metals: theory and experiment
In this paper, we review theoretical and experimental research on rare region
effects at quantum phase transitions in disordered itinerant electron systems.
After summarizing a few basic concepts about phase transitions in the presence
of quenched randomness, we introduce the idea of rare regions and discuss their
importance. We then analyze in detail the different phenomena that can arise at
magnetic quantum phase transitions in disordered metals, including quantum
Griffiths singularities, smeared phase transitions, and cluster-glass
formation. For each scenario, we discuss the resulting phase diagram and
summarize the behavior of various observables. We then review several recent
experiments that provide examples of these rare region phenomena. We conclude
by discussing limitations of current approaches and open questions.Comment: 31 pages, 7 eps figures included, v2: discussion of the dissipative
Ising chain fixed, references added, v3: final version as publishe
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