Ground-state ordering of the J1 - J2 model on the simple cubic and body-centered cubic lattices

The J1−J2 Heisenberg model is a “canonical” model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1−J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p=z2J2/z1J1, where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p=0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p=0.55. Thus the strong frustration present in the J1−J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model

From sea surface to seafloor: A benthic allochthonous eDNA survey for the abyssal ocean

Environmental DNA (eDNA) metabarcoding could facilitate rapid and comprehensive biotic surveys in the deep ocean, yet many aspects of the sources and distribution of eDNA in the deep sea are still poorly understood. In order to examine the influence of the water column on benthic eDNA surveys in regions targeted for deep-sea polymetallic nodule mining, we investigated the occurrence of pelagic eDNA across: (1) two different deep-sea habitat types, abyssal plains and seamounts, (2) benthic sample types, including nodules, sediment, and seawater within the benthic boundary layer (BBL), and (3) sediment depth horizons (0–2 and 3–5 cm). Little difference was observed between seamounts and the adjacent abyssal plains in the proportion of legacy pelagic eDNA sampled in the benthos, despite >1,000 m depth difference for these habitats. In terms of both reads and amplicon sequence variants (ASVs), pelagic eDNA was minimal within sediment and nodule samples (<2%), and is unlikely to affect benthic surveys that monitor resident organisms at the deep seafloor. However, pelagic eDNA was substantial within the BBL (up to 13% ASVs, 86% reads), derived both from the high-biomass upper ocean as well as deep pelagic residents. While most pelagic metazoan eDNA found in sediments and on nodules could be sourced from the epipelagic, protist legacy eDNA sampled on these substrates appeared to originate across a range of depths in the water column. Some evidence of eDNA degradation across a vertical sediment profile was observed for protists, with higher diversity in the 0–2 cm layer and a significantly lower proportion of legacy pelagic eDNA in deeper sediments (3–5 cm). Study-wide, our estimated metazoan sampling coverage ranged from 40 to 74%, despite relatively large sample size. Future deep-sea eDNA surveys should examine oceanographic influences on eDNA transport and residence times, consider habitat heterogeneity at a range of spatial scales in the abyss, and aim to process large amounts of material per sample (with replication) in order to increase the sampling coverage in these diverse deep ocean communities.publishedVersio

Conversational natural language interaction for place-related knowledge acquisition

We focus on the problems of using Natural Language inter- action to support pedestrians in their place-related knowledge acquisi- tion. Our case study for this discussion is a smartphone-based Natu- ral Language interface that allows users to acquire spatial and cultural knowledge of a city. The framework consists of a spoken dialogue-based information system and a smartphone client. The system is novel in com- bining geographic information system (GIS) modules such as a visibility engine with a question-answering (QA) system. Users can use the smart- phone client to engage in a variety of interleaved conversations such as navigating from A to B, using the QA functionality to learn more about points of interest (PoI) nearby, and searching for amenities and tourist attractions. This system explores a variety of research questions involving Natural Language interaction for acquisition of knowledge about space and place

Ground-state properties of the triangular-lattice Heisenberg antiferromagnet with arbitrary spin quantum number s

We apply the coupled cluster method to high orders of approximation and exact diagonalizations to study the ground-state properties of the triangular-lattice spin-s Heisenberg antiferromagnet. We calculate the fundamental ground-state quantities, namely, the energy e0, the sublattice magnetization Msub, the in-plane spin stiffness ρs and the in-plane magnetic susceptibility χ for spin quantum numbers s=1/2,1,…,smax, where smax=9/2 for e0 and Msub, smax=4 for ρs and smax=3 for χ . We use the data for s≥3/2 to estimate the leading quantum corrections to the classical values of e0, Msub, ρs, and χ. In addition, we study the magnetization process, the width of the 1/3 plateau as well as the sublattice magnetizations in the plateau state as a function of the spin quantum number s

Effect of a prebiotic mixture on intestinal comfort and general wellbeing in health

Specific carbohydrates, i.e. prebiotics such as fructo-oligosaccharide (FOS), are not digested in the small intestine but fermented in the colon. Besides beneficial health effects of an enhanced bifidobacteria population, intestinal gas production resulting from fermentation can induce abdominal symptoms. Partial replacement with slowly fermented acacia gum may attenuate side effects. The aim was to compare the effects of FOS with those of a prebiotic mixture (50% FOS and 50% acacia gum; BLEND) and a rapidly absorbed carbohydrate (maltodextrin) on general intestinal wellbeing, abdominal comfort and anorectal sensory function. Twenty volunteers (eight male and twelve female; age 20-37 years) completed this double-blind, randomised study with two cycles of a 2-week run-in phase (10g maltodextrin) followed by 5 weeks of 10g FOS or BLEND once daily, separated by a 4-week wash-out interval. Abdominal symptoms and general wellbeing were documented by telephone interview or Internet twice weekly. Rectal sensations were assessed by a visual analogue scale during a rectal barostat test after FOS and BLEND treatment. Both FOS and BLEND induced more side effects than maltodextrin. Belching was more pronounced under FOS compared with BLEND (P=0·09 for females; P=0·01 for males), and for self-reported general wellbeing strong sex differences were reported (P=0·002). Urgency scores during rectal barostat were higher with FOS than BLEND (P=0·01). Faced with a growing range of supplemented food products, consumers may benefit from prebiotic mixtures which cause fewer abdominal side effects. Sex differences must be taken in consideration when food supplements are use

Percutaneous endobiliary forceps biopsy of biliary strictures for histopathologic examination

PURPOSEWe aimed to investigate the feasibility, accuracy and safety of percutaneous endobiliary cholangio-forceps biopsy of biliary strictures in our institution.METHODSA total of 13 percutaneous transhepatic endobiliary biopsies (7 men and 6 women, mean age 66.85±16.76 years) were performed between January 2015 and March 2019 using a transluminal forceps biopsy device. Technical success, rate of complications, number of biopsy specimens, procedure and fluoroscopy time, mean radiation exposure were evaluated; sensitivity and accuracy were calculated.RESULTSTechnical success, i.e., acquisition of at least three (median, 3.00; range, 3–5) macroscopic representative samples, could be achieved in all 13 biopsies. Access was gained via the right liver lobe in 12 of 13 cases (92.3%). All patients presented blood work indicative of cholestasis prior the intervention, with mean bilirubin 4.72±3.72 µmol/L, mean γ-glutamyl transferase 574.16 ± 360.92 IU/L, and median alkaline phosphatase 407 IU/L (165–1366 IU/L). In 12 of 13 cases (92.3%), biopsied material was sufficient for the pathologist to make a histopathologic diagnosis. Analysis revealed cases of malignancy in eight of 13 cases (61.5%), all of which turned out to be cases of cholangiocarcinoma. In four benign cases (30.8%), diagnosis was considered to be confirmed by further imaging or clinical follow-ups, which showed no signs of progressive disease. There was one case (7.7%) of a false-negative result with proof of malignancy in subsequent surgical tissue extraction. A calculation of diagnostic performance yielded a sensitivity rate of 88.9% and an accuracy rate of 92.3%. There was one case of minor and one case of major complication in our study collective, leading to an overall complication rate of 15.4%.CONCLUSIONPercutaneous transhepatic biliary drainage (PTBD)-based forceps biopsy via the transhepatic drainage tract in patients with biliary obstruction of unknown origin is a technically feasible and safe technique with good diagnostic value rates. The procedure should be considered in patients not suitable for endoscopic strategies with indication for establishment of PTBD

Hepatic mitochondrial dysfunction in Friedreich Ataxia

<p>Abstract</p> <p>Background</p> <p>Mitochondrial dysfunction due to respiratory chain impairment is a key feature in pathogenesis of Friedreich ataxia. Friedreich ataxia affects the nervous system, heart and pancreas.</p> <p>Methods</p> <p>We assessed hepatic mitochondrial function by ¹³C-methionine-breath-test in 16 Friedreich ataxia patients and matched healthy controls.</p> <p>Results</p> <p>Patients exhaled significantly smaller amounts of ¹³CO₂over 90 minutes. Maximal exhaled percentage dose of ¹³CO₂recovery was reduced compared to controls.</p> <p>Conclusions</p> <p>¹³C-methionine-breath-test indicates subclinical hepatic mitochondrial dysfunction in Friedreich ataxia but did not correlate with GAA repeat lengths, disease duration or disease severity.</p

Diversity of Phylogenetic Information According to the Locus and the Taxonomic Level: An Example from a Parasitic Mesostigmatid Mite Genus

Molecular markers for cladistic analyses may perform differently according to the taxonomic group considered and the historical level under investigation. Here we evaluate the phylogenetic potential of five different markers for resolving evolutionary relationships within the ectoparasitic genus Dermanyssus at the species level, and their ability to address questions about the evolution of specialization. COI provided 9–18% divergence between species (up to 9% within species), 16S rRNA 10–16% (up to 4% within species), ITS1 and 2 2–9% (up to 1% within species) and Tropomyosin intron n 8–20% (up to 6% within species). EF-1α revealed different non-orthologous copies within individuals of Dermanyssus and Ornithonyssus. Tropomyosin intron n was shown containing consistent phylogenetic signal at the specific level within Dermanyssus and represents a promising marker for future prospects in phylogenetics of Acari. Phylogenetic analyses revealed that the generalist condition is apomorphic and D. gallinae might represent a complex of hybridized lineages. The split into hirsutus-group and gallinae-group in Dermanyssus does not seem to be appropriate based upon these results and D. longipes appears to be composed of two different entities

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong