The characteristic gamma spectrums of different elements stimulated by neutrons have been studied using Geant4 (Geant4.7.0, 2005), a Monte Carlo simulation software. The results show that for different incident neutrons, the yield of different characteristic gamma photons are variational, from which the conception of optimal incident neutron energy is suggested. These results indicate that optimal energy for different elements is varied and the energies of characteristic gamma photons for all the elements are mainly in the range of 0.8-7 MeV. (authors)
Positron annihilation lifetime spectroscopy (PALS) is a powerful technique to study the free volume in polymers. The lifetime of ortho-positronium (o-Ps), a bound state of an electron and a positron, can be used to assess the pore size while the intensity can be used to characterize the number of pores. On the basis of the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes in the sulfonated poly (2,6-dimethyl-1,4-phenyleneoxide) (SPPO) membranes with different amounts of LiCl were calculated. It was found that, with the increasing amount of LiCl, the free volume radius and the fractional free volume firstly increased and then decreased. After immersing the membranes in distilled water, the free volume radius and the fractional free volume changed with different water concentrations in the membrane.
Objectives: Since netrin-1 and its receptor deleted in colorectal cancer (DCC) are important regulators in neuronal and vascular activities, the present study attempted to explore whether netrin-1 and DCC are involved in the neuroprotection of stem cell-based therapies in a rat ischemic stroke model. Methods: Adult male rats were subjected to a transient middle cerebral artery occlusion (MCAO) and subsequently received an intra-arterial injection of 2 × 10^6 PKH26-labeled adipose-derived stem cells (ADSCs) or saline 24 h later. Neurological function was evaluated before the rats were sacrificed at days 7 and 14 after MCAO. The migration of ADSCs and regeneration of neuronal fibers and blood vessels were determined by immunofluorescence staining. The expression of netrin-1 and DCC was analyzed by Western blot and immunofluorescence staining. Results: ADSC transplantation significantly improved the neurological recovery at days 7 and 14, and noticeably promoted the regeneration of neuronal fibers and blood vessels in the peri-infarct cortex at day 14. PKH26-labeled ADSCs located mainly in the peri-infarct area at days 7 and 14. In ADSC-treated rats, the expression of netrin-1 and DCC significantly increased in the peri-infarct cortex at days 7 and 14. Immunofluorescence staining showed that netrin-1 was mainly expressed by neuronal perikaryal in the peri-infarct cortex, and DCC was mainly expressed by neuronal fibers and was present around the blood vessels in the peri-infarct cortex. Conclusion: ADSC transplantation facilitates the regeneration of neuronal fibers and blood vessels in the peri-infarct cortex and improves neurological functions, which may be attributed, at least in part, to the involvement of upregulated netrin-1 and DCC in the remodeling of neuronal and vascular networks in the peri-infarct cortex.
Constructing the recombinant Listeria ivanovii strain expressing green fluorescent protein to provide an important tool for study of Listeria ivanovii.The promoter of Listeria monocytogenes Listeriolysin O (phly) and the green fluorescent protein (GFP) gene were fused by SOEing PCR,and then ligated the fusion gene into plasmid pCW to result in recombinant plasmid pCW-phly-GFP. Recombinant plasmid was electroporated into Listeria ivanovii,and fluorescence microscope was used to analyze the expression of GFP. To observe the stability of recombinant plasmid and the stable expression of GFP in Listeria ivanovii,bacteria were cultured in the BHI broth with or without erythromycin for several generations. The stability of recombinant plasmid pCW-phly-GFP and fluorescent protein in each generation of bacteriawas studied by extracting plasmids and observing fluorescence.The exactness of recombinant plasmid pCW-phly-GFP was confirmed with restrictive endonuclease assay and sequence analysis. Under the fluorescence microscope,the green fluorescence was obvious in Listeria ivanovii carried with pCW-phly-GFP. The recombinant plasmid pCW-phly-GFP was stable in Listeria ivanovii and the GFP kept expressing in a high level under the pressure of erythromycin.The prokaryotic expression plasmid pCW-phly-GFP containing GFP gene was successfully constructed. Listeria ivanovii carried with the plasmid efficiently expressed GFP. This research provides an important tool for further study of Listeria ivanovii as a vaccine carrier.
The risk factors associated with iodine contrast extravasation immediately after endovascular thrombectomy (EVT) and subsequent hemorrhagic transformation within 24 hours remain unclear.Mixed images, iodine overlay maps, and virtual non-contrast images were reconstructed from 106 consecutive acute ischemic stroke patients who underwent dual energy computed tomography immediately and 24 hours after EVT. Multivariate analyses of clinical and radiological data were performed to explore independent predictors of iodine contrast extravasation and hemorrhagic transformation.Sixty-eight (64.2%) patients exhibited pure iodine contrast extravasation after EVT; 30.9% developed hemorrhagic transformation within 24 hours after EVT. The number of stent retriever passes was independently associated with both iodine contrast extravasation (odds ratio 1.608; 95% confidence interval (CI) 1.047-2.469) and subsequent hemorrhagic transformation (odds ratio 1.477; 95% CI 1.003-2.175). Patients with more than two stent retriever passes were more likely to exhibit iodine contrast extravasation (sensitivity = 68.2%, specificity = 81.5%), while those with more than three stent retriever passes more often exhibited hemorrhage after iodine contrast extravasation (sensitivity = 64.6%, specificity = 87.2%).The number of stent retriever passes was an independent predictor for both iodine contrast extravasation and subsequent hemorrhagic transformation.
Supramolecular hydrogels (SMHs) are three‐dimensional networks filled with a large amount of water. The crosslinking force in the 3D network is always constructed by relatively weak and dynamic non‐covalent interactions, and thus SMHs usually possess extremely high susceptibility to external environment and can show extraordinary stimuli‐responsive, self‐healing or other attractive properties. However, the overall crosslinking force in hydrogel networks is difficult to flexibly modulate, and this leads to limited functions of the SMHs. In this regard, hierarchical hydrogen bonds, that is, the mixture of relatively strong and relatively weak hydrogen bonds, are used herein as crosslinking force for the hydrogel preparation. The ratio of strong and weak hydrogen bonds can be finely tuned to tailor the properties of resultant gels. Thus, by delicate manipulation of the overall crosslinking force in the system, a hydrogel with multiple (thermal, pH and NIR light) responsiveness, autonomous self‐healing property and interesting temperature dependent, reversible adhesion behavior is obtained. This kind of hierarchical hydrogen bond manipulation is proved to be a general method for multiple‐functionality hydrogel preparation, and the resultant material shows potential for a range of applications.
Learning from nature has garnered significant attention in the scientific community for its potential to inspire creative solutions in material or catalyst design. The study reports a biomimetic single selenium (Se) site‐modified carbon (C) moiety that retains the unique reactivity of selenoenzyme with peroxides, aiming to selectively catalyze the oxygen reduction reaction (ORR). The as‐designed Se‐C demonstrates nearly 100% 4‐electron selectivity, evidenced by 0.039% of H2O2 yield at 0.5 V versus reversible hydrogen electrode, outperforming commercial platinum (Pt) by 65 times. In‐situ X‐ray absorption spectroscopy and theoretical calculations attribute this exceptional selectivity to the enzyme‐like behaviors of the Se site to steal an O atom from peroxide intermediates. The second achievement is the significantly increased consecutive 2+2 electron selectivity. Benefiting from the enzyme‐like H2O2 reduction activity with a higher onset potential of 0.915 V compared to Pt at 0.875 V, the Se‐C as a secondary catalytic site reduced the H2O2 yields of the Co‐N‐C, Fe‐N‐C, and N‐C catalysts by 96%, 67%, and 98%, respectively, via a consecutive 2+2 electron pathway. This also leads to more stable catalysts via protecting the active sites from oxidative attacks. This work establishes new pathways for precise tuning of reaction selectivity in ORR and beyond.
Gadofullerenes derivatives had been proved to exhibit high relaxivities, even higher than that of commercial Gd-DTPA contrast agents. However, all reported gadofullerene contrast agents were based on the functionalized metallofullerene. In this presentation, we successfully constructed novel water-soluble carbon nanohybrids based on unmodified metallofullerene and graphene oxide, which exhibited high relaxivity and better brightening effect in magnetic resonance (MR) imaging in vivo. Gd@C 82 was produced and isolated by the industrial-scale production line of metallofullerenes firstly established in Institute of High Energy Physics, Chinese Academy of Science (CAS). A “secondary spin-electron transfer” relaxation mechanism was proposed to explain how the encaged Gd 3+ ions of carbon nanohybrids interact with the surrounding water molecules. This approach opens new opportunities in developing highly efficient and low toxic MRI contrast agent. Figure 1
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