4,789 research outputs found

    Cosmological investigation of multi-frequency VLBI observations of ultra-compact structure in zāˆ¼3z\sim 3 radio quasars

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    In this paper, we use multi-frequency angular size measurements of 58 intermediate-luminosity quasars reaching the redshifts zāˆ¼3z\sim 3 and demonstrate that they can be used as standard rulers for cosmological inference. Our results indicate that, for the majority of radio-sources in our sample their angular sizes are inversely proportional to the observing frequency. From the physical point of view it means that opacity of the jet is governed by pure synchrotron self-absorption, i.e. external absorption does not play any significant role in the observed angular sizes at least up to 43 GHz. Therefore, we use the value of the intrinsic metric size of compact milliarcsecond radio quasars derived in a cosmology independent manner from survey conducted at 2 GHz and rescale it properly according to predictions of the conical jet model. This approach turns out to work well and produce quite stringent constraints on the matter density parameter Ī©m\Omega_m in the flat Ī›\LambdaCDM model and Dvali-Gabadadze-Porrati braneworld model. The results presented in this paper pave the way for the follow up engaging multi-frequency VLBI observations of more compact radio quasars with higher sensitivity and angular resolution.Comment: 10 pages, 5 figures, 2 table, accepted for publication in European Physical Journal

    The influence of protein free calf blood extract eye gel on dry eye after pterygium surgery

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    AIM: To investigate the influence of protein free calf blood extract eye gel on dry eye after pterygium surgery. <p>METHODS: Thirty six patients(40 eyes)with primary nasal pterygium were enrolled in this study, which were divided into study group and control group randomly, with 20 eyes in each group. All patients received pterygium excision and limbal stem cell autograft surgery and tobramicin dexamethasone eye drops after surgery. Patients of the study group received protein free calf blood extract eye gel while those of the control group received 0.1% sodium hyaluronate eye drops furthermore. Ocular surface disease index(OSDI)questionnaire, tear film break-up time(BUT)and Schirmer's ā…  test ā… (Sā… t)were carried before and 3 months after surgery to evaluate the dry eye degree of the patients. <p>RESULTS: There was no statistical difference between the age, gender and size of the pterygium of the study and control groups preoperatively. There was no statistical difference between the OSDI(2.33Ā±1.02 <i>vs</i> 2.32Ā±0.93), BUT(8.80Ā±2.48 <i>vs</i> 8.35Ā±2.28)seconds and Sā… t(4.30Ā±2.30 <i>vs</i> 4.40Ā±2.44)of the two groups preoperatively. There was statistical difference between the OSDI(1.45Ā±0.47 <i>vs</i> 1.81Ā±0.60), BUT(11.20Ā±2.07 <i>vs</i> 9.50Ā±2.40)seconds and Sā… t(8.35Ā±3.13 <i>vs</i> 6.35Ā±2.18)of the two groups 3 months postoperatively, which was also different from that of the preoperative data correspondingly. <p>CONCLUSION: Protein free calf blood extract eye gel could reduce the dry eye after pterygium surgery

    A review of ammonia-oxidizing bacteria and archaea in Chinese soils

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    Ammonia (NH3) oxidation, the first and rate-limiting step of nitrification, is a key step in the global Nitrogen (N) cycle. Major advances have been made in recent years in our knowledge and understanding of the microbial communities involved ammonia oxidation in a wide range of habitats, including Chinese agricultural soils. In this mini-review, we focus our attention on the distribution and community diversity of ammonia-oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) in Chinese soils with variable soil properties and soil management practices. The niche differentiation of AOB and AOA in contrasting soils have been functionally demonstrated using DNA-SIP (stable isotope probing) methods, which have shown that AOA dominate nitrification processes in acidic soils, while AOB dominated in neutral, alkaline and N-rich soils. Finally, we discuss the composition and activity of ammonia oxidizer in paddy soils, as well as the mitigation of the greenhouse gas nitrous oxide (N2O) emissions and nitrate leaching via inhibition of nitrification by both AOB and AOA

    Functional Source Separation for EEG-fMRI Fusion: Application to Steady-State Visual Evoked Potentials

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    Neurorobotics is one of the most ambitious fields in robotics, driving integration of interdisciplinary data and knowledge. One of the most productive areas of interdisciplinary research in this area has been the implementation of biologically-inspired mechanisms in the development of autonomous systems. Specifically, enabling such systems to display adaptive behavior such as learning from good and bad outcomes, has been achieved by quantifying and understanding the neural mechanisms of the brain networks mediating adaptive behaviors in humans and animals. For example, associative learning from aversive or dangerous outcomes is crucial for an autonomous system, to avoid dangerous situations in the future. A body of neuroscience research has suggested that the neurocomputations in the human brain during associative learning involve re-shaping of sensory responses. The nature of these adaptive changes in sensory processing during learning however are not yet well enough understood to be readily implemented into on-board algorithms for robotics application. Toward this overall goal, we record the simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), characterizing one candidate mechanism, i.e., large-scale brain oscillations. The present report examines the use of Functional Source Separation (FSS) as an optimization step in EEG-fMRI fusion that harnesses timing information to constrain the solutions that satisfy physiological assumptions. We applied this approach to the voxel-wise correlation of steady-state visual evoked potential (ssVEP) amplitude and blood oxygen level-dependent imaging (BOLD), across both time series. The results showed the benefit of FSS for the extraction of robust ssVEP signals during simultaneous EEG-fMRI recordings. Applied to data from a 3-phase aversive conditioning paradigm, the correlation maps across the three phases (habituation, acquisition, extinction) show converging results, notably major overlapping areas in both primary and extended visual cortical regions, including calcarine sulcus, lingual cortex, and cuneus. In addition, during the acquisition phase when aversive learning occurs, we observed additional correlations between ssVEP and BOLD in the anterior cingulate cortex (ACC) as well as the precuneus and superior temporal gyrus

    Interaction of a symmetrical Ī±,Ī±',Ī“,Ī“'-Tetramethyl-cucurbit[6]uril with LnĀ³āŗ : potential applications for isolation of lanthanides

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    The interaction of a symmetrical Ī±,Ī±ā€²,Ī“,Ī“ā€²-tetramethyl-cucurbit[6]uril (TMeQ[6]) with a series of lanthanide cations (LnĀ³āŗ) was investigated in neutral water and in acidic solution. Analysis by single crystal X-ray diffraction revealed that different isomorphous families formed under different synthetic conditions. Such differences in the interaction between TMeQ[6] and LnĀ³āŗ could potentially be used for isolating heavier LnĀ³āŗ from their lighter counterparts in neutral solution, and lighter lanthanide cations from their heavier counterparts in acidic solution

    The impact of single nucleotide polymorphism in monomeric alpha-amylase inhibitor genes from wild emmer wheat, primarily from Israel and Golan

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    <p>Abstract</p> <p>Background</p> <p>Various enzyme inhibitors act on key insect gut digestive hydrolases, including alpha-amylases and proteinases. Alpha-amylase inhibitors have been widely investigated for their possible use in strengthening a plant's defense against insects that are highly dependent on starch as an energy source. We attempted to unravel the diversity of monomeric alpha-amylase inhibitor genes of Israeli and Golan Heights' wild emmer wheat with different ecological factors (e.g., geography, water, and temperature). Population methods that analyze the nature and frequency of allele diversity within a species and the codon analysis method (comparing patterns of synonymous and non-synonymous changes in protein coding sequences) were used to detect natural selection.</p> <p>Results</p> <p>Three hundred and forty-eight sequences encoding monomeric alpha-amylase inhibitors (WMAI) were obtained from 14 populations of wild emmer wheat. The frequency of SNPs in WMAI genes was 1 out of 16.3 bases, where 28 SNPs were detected in the coding sequence. The results of purifying and the positive selection hypothesis (p < 0.05) showed that the sequences of WMAI were contributed by both natural selection and co-evolution, which ensured conservation of protein function and inhibition against diverse insect amylases. The majority of amino acid substitutions occurred at the C-terminal (positive selection domain), which ensured the stability of WMAI. SNPs in this gene could be classified into several categories associated with water, temperature, and geographic factors, respectively.</p> <p>Conclusions</p> <p>Great diversity at the WMAI locus, both between and within populations, was detected in the populations of wild emmer wheat. It was revealed that WMAI were naturally selected for across populations by a ratio of dN/dS as expected. Ecological factors, singly or in combination, explained a significant proportion of the variations in the SNPs. A sharp genetic divergence over very short geographic distances compared to a small genetic divergence between large geographic distances also suggested that the SNPs were subjected to natural selection, and ecological factors had an important evolutionary role in polymorphisms at this locus. According to population and codon analysis, these results suggested that monomeric alpha-amylase inhibitors are adaptively selected under different environmental conditions.</p
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