Most of the resting-state functional magnetic resonance imaging (fMRI) studies demonstrated the correlations between spatially distinct brain areas from the perspective of functional connectivity or ...functional integration. The functional connectivity approaches do not directly provide information of the amplitude of brain activity of each brain region within a network. Alternatively, an index named amplitude of low-frequency fluctuation (ALFF) of the resting-state fMRI signal has been suggested to reflect the intensity of regional spontaneous brain activity. However, it has been indicated that the ALFF is also sensitive to the physiological noise. The current study proposed a fractional ALFF (fALFF) approach, i.e., the ratio of power spectrum of low-frequency (0.01–0.08
Hz) to that of the entire frequency range and this approach was tested in two groups of resting-state fMRI data. The results showed that the brain areas within the default mode network including posterior cingulate cortex, precuneus, medial prefrontal cortex and bilateral inferior parietal lobule had significantly higher fALFF than the other brain areas. This pattern was consistent with previous neuroimaging results. The non-specific signal components in the cistern areas in resting-state fMRI were significantly suppressed, indicating that the fALFF approach improved the sensitivity and specificity in detecting spontaneous brain activities. Its mechanism and sensitivity to abnormal brain activity should be evaluated in the future studies.
In children with attention deficit hyperactivity disorder (ADHD), functional neuroimaging studies have revealed abnormalities in various brain regions, including prefrontal-striatal circuit, ...cerebellum, and brainstem. In the current study, we used a new marker of functional magnetic resonance imaging (fMRI), amplitude of low-frequency (0.01–0.08
Hz) fluctuation (ALFF) to investigate the baseline brain function of this disorder. Thirteen boys with ADHD (13.0
±
1.4 years) were examined by resting-state fMRI and compared with age-matched controls. As a result, we found that patients with ADHD had decreased ALFF in the right inferior frontal cortex, left sensorimotor cortex, and bilateral cerebellum and the vermis as well as increased ALFF in the right anterior cingulated cortex, left sensorimotor cortex, and bilateral brainstem. This resting-state fMRI study suggests that the changed spontaneous neuronal activity of these regions may be implicated in the underlying pathophysiology in children with ADHD.
The high fracture toughness of mollusk nacre is predominantly attributed to the structure‐associated extrinsic mechanisms such as platelet sliding and crack deflection. While the nacre‐mimetic ...structures are widely adopted in artificial ceramics, the extrinsic mechanisms are often weakened by the relatively low tensile strength of the platelets with a large aspect ratio, which makes the fracture toughness of these materials much lower than expected. Here, it is demonstrated that the fracture toughness of artificial nacre materials with high inorganic contents can be improved by residual stress‐induced platelet strengthening, which can catalyze more effective extrinsic toughening mechanisms that are specific to the nacre‐mimetic structures. Thereby, while the absolute fracture toughness of the materials is not comparable with advanced ceramic‐based composites, the toughness amplification factor of the material reaches 16.1 ± 1.1, outperforming the state‐of‐the‐art biomimetic ceramics. The results reveal that, with the merit of nacre‐mimetic structural designs, the overall fracture toughness of the artificial nacre can be improved by the platelet strengthening through extrinsic toughening mechanisms, although the intrinsic fracture toughness may decrease at platelet level due to the strengthening. It is anticipated that advanced structural ceramics with exceeding performance can be fabricated through these unconventional strategies.
This work illustrates an anti‐intuitive strategy that, with the merit of biomimetic designs, residual stress that is conventionally harmful to ceramics can inversely help improve the fracture toughness of biomimetic ceramics through nanoscale residual stress‐induced platelet strengthening. This provides new insights into the design principles of nacre‐like materials at the bottom level.
A PdII‐catalyzed asymmetric aminohydroxylation of 1,3‐dienes with N‐tosyl‐2‐aminophenols was developed by making use of a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction ...provides direct and efficient access to chiral 3,4‐dihydro‐2H‐1,4‐benzoxazines in high yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N‐tosyl‐2‐aminophenols as a unique aminohydroxylation reagent and is complementary to known asymmetric aminohydroxylation methods.
Give me a ring: A palladium‐catalyzed asymmetric aminohydroxylation reaction of 1,3‐dienes with N‐tosyl‐2‐aminophenols was developed by employing a chiral pyridinebis(oxazoline) ligand. This reaction furnishes optically active 3,4‐dihydro‐2H‐1,4‐benzoxazines in high yields and with high levels of regio‐ and stereoselectivity.
In the fields of industry research, infrared spectrometers are widely used in diverse applications. However, the spectrum often suffers from band overlap and random noise due to the distortion caused ...by the point spread function, especially for aging instruments. The problem of reconstructing the clear spectrum from the degraded spectrum is called spectrum deconvolution. Traditional partial differential equation (PDE) methods rely on distribution assumptions in the reconstructed process. This restriction makes PDE methods sensitive to tackle complex instrumental broadening effect in the dispersive IR spectrometers. Also, we need to spend much time setting the parameters of PDE models manually. These problems intuitively degrade the performances of PDE methods. In this article, we propose an end-to-end neural network framework for spectral deconvolution problem. The novelty of this article lies in its strong robustness from dilated deconvolution and self-paced learning procedure to challenge the complicated degraded spectra. Actually, the deconvolution problem is tailored to a dense prediction problem in this article. Inspired by the extensive use and excellent effects of dilated convolutions in dense prediction, a lightweight dilated convolution module is given to detect the overlaps of degraded spectra. Experimental results demonstrate that the proposed solution has an outstanding performance against many other approaches. Such improvements have the potential to facilitate industrial applications and further exploration of an unknown chemical mixture. Our framework has a good performance on feature extracting and spectrum reconstruction, even in the case of low signal-to-noise ratio.
Resting-state fMRI (RS-fMRI) has been drawing more and more attention in recent years. However, a publicly available, systematically integrated and easy-to-use tool for RS-fMRI data processing is ...still lacking. We developed a toolkit for the analysis of RS-fMRI data, namely the RESting-state fMRI data analysis Toolkit (REST). REST was developed in MATLAB with graphical user interface (GUI). After data preprocessing with SPM or AFNI, a few analytic methods can be performed in REST, including functional connectivity analysis based on linear correlation, regional homogeneity, amplitude of low frequency fluctuation (ALFF), and fractional ALFF. A few additional functions were implemented in REST, including a DICOM sorter, linear trend removal, bandpass filtering, time course extraction, regression of covariates, image calculator, statistical analysis, and slice viewer (for result visualization, multiple comparison correction, etc.). REST is an open-source package and is freely available at http://www.restfmri.net.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The catalytic C–F bond carboxylation of organofluorines with CO2 gas remains a challenging problem in synthetic chemistry. Here, we describe a selective defluorinative carboxylation of ...gem-difluoroalkenes through photoredox/palladium dual catalysis. The C–F bond activation is enabled by single electron reduction through photoredox catalysis to generate a fluorovinyl radical, which subsequently participates in an unprecedented palladium-catalyzed carboxylation. This novel C–F functionalization proved applicable to a wide range of substituted gem-difluoroalkenes, providing a rapid access to valuable α-fluoroacrylic acids.
Harnessing the physiochemical properties and enzymatic activities of nanozymes will provide new insights for disease theranostics. Herein, a novel carbon dot (C‐dot) superoxide dismutase (SOD) ...nanozyme that exhibits red fluorescence with emission wavelength of 683 nm and shows high SOD‐like activity of >4000 U mg−1 is reported, which presents the great potential for imaging the biodistribution of nanozyme itself in vivo and ameliorating acute lung injury. Through surface modifications, the mechanism of C‐dot SOD nanozyme activity is revealed to be relied on their surface functional groups which bind with superoxide radicals, promote the electron transfer between C‐dots and superoxide radicals, and finally accelerate the dismutation of superoxide radicals. The absolute quantum yield of ≈14% of red fluorescence C‐dot nanozyme endow it bioimaging in vitro and in vivo. Moreover, the C‐dot nanozyme effectively enters the cells, accumulates at mitochondria, and protects living cells from oxidative damage by scavenging reactive oxygen species (ROS) and reducing the levels of pro‐inflammatory factors. Importantly, in vivo animal experiments demonstrate the accumulation of C‐dots in injure lung and therapeutic effect of C‐dot nanozyme toward acute lung injury in mice. The red fluorescent C‐dot SOD nanozyme shows great potential for in vivo bioimaging and management of ROS‐related diseases.
Red emissive carbon dot nanozyme with high superoxide dismutase (SOD)‐like activity over 4000 U mg−1 is developed. The SOD nanozyme activity is revealed to be relied on their surface functional groups which capture O2•– and then promote the electron transfer between O2•– and π‐system of carbon dot. The C‐dot SOD nanozyme shows great potential in bioimaging and ameliorating acute lung injury.
Dipolar glass (DG) polymers, which utilize sub-T g orientational polarization (T g is the glass transition temperature) to enhance dielectric constants, are promising candidates for use in advanced ...electronic and power applications because conduction of space charges (electrons and impurity ions) is suppressed in the glassy state, and thus, the dielectric loss is low. In this study, we studied the effects of dipole density and dipole arrangement in sulfonyl-containing side-chain DG polymers on their dielectric performance in terms of dielectric constant, energy density, and dielectric loss. Monosulfonyl (i.e., CH3SO2-) and disulfonyl i.e., CH3SO2(CH2)3SO2- groups were quantitatively grafted to polyepichlorohydrin (monosubstitution) and poly(3,3-bis(chloromethyl)oxatane) (bis-substitution), respectively, in order to vary the dipole density and dipole arrangement in the side chains. As a result of orientation polarization from highly polar sulfonyl (4.5 D) groups, these DG polymers exhibited high apparent dielectric constants (7–11.5) in the glassy state with reasonably low dissipation factors (tan δ ∼ 0.003–0.02). It was found that disulfonylated DG polymers exhibited a higher dielectric constant than monosulfonylated DG polymers because of their higher dipole densities. Meanwhile, bis-substituted DG polymers showed a higher dielectric constant than monosubstituted DG polymers. Upon high-field electric poling, reversible transitions between the low-field DG state and the high-field ferroelectric state induced double hysteresis loops, and disulfonylated DG polymers had more significant ferroelectric switching than monosulfonylated DG polymers due to stronger dipolar interactions among the disulfonyl groups. On the basis of the experimental results, monosulfonylated DG polymers, whether mono- or bis-substituted, should be more appropriate for electric energy storage applications.
An efficient Mn-catalyzed aerobic oxidative hydroxyazidation of olefins for synthesis of β-azido alcohols has been developed. The aerobic oxidative generation of azido radical employing air as the ...terminal oxidant is disclosed as the key process for this transformation. The reaction is appreciated by its broad substrate scope, inexpensive Mn-catalyst, high efficiency, easy operation under air, and mild conditions at room temperature. This chemistry provides a novel approach to high value-added β-azido alcohols, which are useful precursors of aziridines, β-amino alcohols, and other important N- and O-containing heterocyclic compounds. This chemistry also provides an unexpected approach to azido substituted cyclic peroxy alcohol esters. A DFT calculation indicates that Mn catalyst plays key dual roles as an efficient catalyst for the generation of azido radical and a stabilizer for peroxyl radical intermediate. Further calculation reasonably explains the proposed mechanism for the control of C–C bond cleavage or for the formation of β-azido alcohols.
PDF
