153 research outputs found

    Recovery of Boundaries and Types for Multiple Obstacles from the Far-field Pattern

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    We consider an inverse scattering problem for multiple obstacles D=j=1NDjR3D=\cup_{j=1}^ND_j\subset {R}^3 with different types of boundary of DjD_j. By constructing an indicator function from the far-field pattern of scattered wave, we can firstly determine the boundary location for all obstacles, then identify the boundary type for each obstacle, as well as the boundary impedance in case of Robin-type obstacles. The reconstruction procedures for these identifications are also given. Comparing with the existing probing method which is applied to identify one obstacle in generally, we should analyze the behavior of both the imaginary part and the real part of the indicator function so that we can identify the type of multiple obstacles

    The genetic determinants of language network dysconnectivity in drug-naïve early stage schizophrenia

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    Schizophrenia is a neurocognitive illness of synaptic and brain network-level dysconnectivity that often reaches a persistent chronic stage in many patients. Subtle language deficits are a core feature even in the early stages of schizophrenia. However, the primacy of language network dysconnectivity and language-related genetic variants in the observed phenotype in early stages of illness remains unclear. This study used two independent schizophrenia dataset consisting of 138 and 53 drug-naïve first-episode schizophrenia (FES) patients, and 112 and 56 healthy controls, respectively. A brain-wide voxel-level functional connectivity analysis was conducted to investigate functional dysconnectivity and its relationship with illness duration. We also explored the association between critical language-related genetic (such as FOXP2) mutations and the altered functional connectivity in patients. We found elevated functional connectivity involving Broca’s area, thalamus and temporal cortex that were replicated in two FES datasets. In particular, Broca’s area - anterior cingulate cortex dysconnectivity was more pronounced for patients with shorter illness duration, while thalamic dysconnectivity was predominant in those with longer illness duration. Polygenic risk scores obtained from FOXP2-related genes were strongly associated with functional dysconnectivity identified in patients with shorter illness duration. Our results highlight the criticality of language network dysconnectivity, involving the Broca’s area in early stages of schizophrenia, and the role of language-related genes in this aberration, providing both imaging and genetic evidence for the association between schizophrenia and the determinants of language

    An In Vivo Functional Screen Uncovers miR-150-Mediated Regulation of Hematopoietic Injury Response

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    SummaryHematopoietic stem and progenitor cells are often undesired targets of chemotherapies, leading to hematopoietic suppression requiring careful clinical management. Whether microRNAs control hematopoietic injury response is largely unknown. We report an in vivo gain-of-function screen and the identification of miR-150 as an inhibitor of hematopoietic recovery upon 5-fluorouracil-induced injury. Utilizing a bone marrow transplant model with a barcoded microRNA library, we screened for barcode abundance in peripheral blood of recipient mice before and after 5-fluorouracil treatment. Overexpression of screen-candidate miR-150 resulted in significantly slowed recovery rates across major blood lineages, with associated impairment of bone marrow clonogenic potential. Conversely, platelets and myeloid cells from miR-150 null marrow recovered faster after 5-fluorouracil treatment. Heterozygous knockout of c-myb, a conserved target of miR-150, partially phenocopied miR-150-forced expression. Our data highlight the role of microRNAs in controlling hematopoietic injury response and demonstrate the power of in vivo functional screens for studying microRNAs in normal tissue physiology

    The impact of cognitive training on cerebral white matter in community-dwelling elderly : one-year prospective longitudinal diffusion tensor imaging study

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    It has been shown that cognitive training (CogTr) is effective and recuperative for older adults, and can be used to fight against cognitive decline. In this study, we investigated whether behavioural gains from CogTr would extend to white matter (WM) microstructure, and whether training-induced changes in WM integrity would be associated with improvements in cognitive function, using diffusion tensor imaging (DTI). 48 healthy community elderly were either assigned to multi-domain or single-domain CogTr groups to receive 24 sessions over 12 weeks, or to a control group. DTI was performed at both baseline and 12-month follow-up. Positive effects of multi-domain CogTr on long-term changes in DTI indices were found in posterior parietal WM. Participants in the multi-domain group showed a trend of long-term decrease in axial diffusivity (AD) without significant change in fractional anisotropy (FA), mean diffusivity (MD) or radial diffusivity (RD), while those in the control group displayed a significant FA decrease, and an increase in MD and RD. In addition, significant relationships between an improvement in processing speed and changes in RD, MD and AD were found in the multi-domain group. These findings support the hypothesis that plasticity of WM can be modified by CogTr, even in late adulthood

    Room-temperature ferromagnetism in epitaxial bilayer FeSb/SrTiO3(001) terminated with a Kagome lattice

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    Two-dimensional (2D) magnets exhibit unique physical properties for potential applications in spintronics. To date, most 2D ferromagnets are obtained by mechanical exfoliation of bulk materials with van der Waals interlayer interactions, and the synthesis of single or few-layer 2D ferromagnets with strong interlayer coupling remains experimentally challenging. Here, we report the epitaxial growth of 2D non-van der Waals ferromagnetic bilayer FeSb on SrTiO3(001) substrates stabilized by strong coupling to the substrate, which exhibits in-plane magnetic anisotropy and a Curie temperature above 300 K. In-situ low-temperature scanning tunneling microscopy/spectroscopy and density-functional theory calculations further reveal that a Fe Kagome layer terminates the bilayer FeSb. Our results open a new avenue for further exploring emergent quantum phenomena from the interplay of ferromagnetism and topology for application in spintronics

    Rapid and sensitive determination of Se and heavy metals in foods using electrothermal vaporization inductively coupled plasma mass spectrometry with a novel transportation system

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    Rapid, sensitive and simultaneous determination of trace multi-elements in various plant food samples such as grain, oilseed, vegetable and tea is always a challenge thus far. In this work, a rapid determination method for Se, Cd, As and Pb in food samples by inductively coupled plasma mass spectrometry (ICP-MS) using slurry sampling electrothermal vaporization (SS-ETV) was developed. To improve the analytical sensitivity and precision as well as eliminate the memory effect, a gas turbulator line and signal delay device (SDD) were for the first time designed for the graphite furnace (GF) ETV coupled with ICP-MS. The signal acquisition parameters of ICP-MS, ashing and vaporization conditions, and the flow rates of carrier gas and gas turbulator were investigated for Se, Cd, As and Pb in food samples. Under the optimized conditions, the limits of determination (LODs) for Se, Cd, As and Pb were 0.5 ng g−1, 0.3 ng g−1, 0.3 ng g−1 and 0.6 ng g−1, respectively; the limits of quantification (LOQs) for Se, Cd, As and Pb were 1.7 ng g−1, 1.0 ng g−1, 1.0 ng g−1 and 1.9 ng g−1, respectively; linearity (R2) in the range of 1 to 4,000 ng g−1 was >0.999 using the standard addition method. This method was used to analyze 5 CRMs including rice, tea and soybeans, and the concentrations detected by this method were within the range of the certified values. The recoveries of Se, Cd, As and Pb in plant food matrices including grain, oilseed, celery, spinach, carrot and tea samples were 86–118% compared to the microwave digestion ICP-MS method; and the relative standard deviations (RSDs) were 1.2–8.9% for real food sample analysis, proving a good precision and accuracy for the simultaneous determination of multi-elements. The analysis time was less than 3 min, slurry preparation time < 5 min without sample digestion process. The proposed direct slurry sampling ICP-MS method is thus suitable for rapid and sensitive determination of Se, Cd, As and Pb in food samples with advantages such as simplicity, green and safety, as well as with a promising application potential in detecting more elements to protect food safety and human health

    Electronic and magnetic properties of multishell Co nanowires coated with Cu

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    The structural, electronic, and magnetic properties of ultrathin Cu-coated Co nanowires have been studied by using empirical genetic algorithm simulations and a tight-binding spdspd model Hamiltonian in the unrestricted Hartree-Hock approximation. For some specific stoichiometric compositions, Cu atoms occupy the surface, while Co atoms prefer to stay in the interior, forming the perfect coated multishell structures. The outer Cu layers lead to substantial variations of the magnetic moment of interior Co atoms, depending on the structure and thickness of Cu layers. In particular, single Co atom row in the center of nanowire is found to be nonmagnetic when coated with two Cu layers. All the other Co nanowires in the coated Cu shell are still magnetic but the magnetic moments are reduced as compared with Co nanowires without Cu coating. The interaction between Cu and Co atoms induces nonzero magnetic moment for Cu atoms.Comment: 7 pages, 2 fugure

    Advanced progress on χ(3) nonlinearity in chip-scale photonic platforms

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    χ(3) nonlinearity enables ultrafast femtosecond scale light-to-light coupling and manipulation of intensity, phase, and frequency. χ(3) nonlinear functionality in micro-and nano-scale photonic waveguides can potentially replace bulky fiber platforms for many applications. In this Review, we summarize and comment on the progress on χ(3) nonlinearity in chip-scale photonic platforms, including several focused hot topics such as broadband and coherent sources in the new bands, nonlinear pulse shaping, and all-optical signal processing. An outlook of challenges and prospects on this hot research field is given at the end
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