Results 1 - 10 of 148
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[en] A highly efficient and CO tolerant PtRu electrocatalysts supported on amino-rich, cationic poly(ethyleneimine) polyelectrolyte functionalized multi-walled carbon nanotubes (PtRu/PEI-MWCNTs) has been developed. The catalysts were characterized by thermogravimetric analysis, Raman spectroscopy, cyclic voltammograms, CO stripping, chronoamperometry, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The PtRu particles with average size ∼2.5 nm are well dispersed on PEI-MWCNTs. The peak current for the methanol oxidation reaction on 40% PtRu/PEI-MWCNTs is 636mAmgPt−1, 5.7 times higher than 112mA mgPt−1 measured on the 40% PtRu supported on acid treated MWCNTs (PtRu/AO-MWCNTs) under identical conditions. PtRu/PEI-MWCNTs catalysts exhibit a superior electrocatalytic activity and stability for the methanol oxidation reaction due to its high tolerance toward CO poisoning as compared with PtRu/AO-MWCNTs for direct methanol fuel cells
[en] The Schwinger-Dyson loop equations for the hermitian multi-matrix chain models at finite N, are derived from the Ward identities of the partition functional under the infinitesimal field transformations. The constraint operators Wn(m) satisfy the w1+∞-like algebra up to a linear combination of the lower spin operators. We find that the all the higher spin constraints are reducible to the Virasoro-type constraints for all the matrix chain models. (author)
[en] A detailed chemical kinetic mechanism based on the Appel-Bockhorn-Frenklach (ABF) model was established to describe acetylene decomposition, ethylene formation, and soot formation during quenching in coal pyrolysis to acetylene process. The predictions agreed well with the reported acetylene pyrolysis experimental data. Numerical simulations were then performed to deeply understand the reaction behaviors during quenching of coal pyrolysis in thermal plasma, and to optimize the quenching design for better heat recovery. Two key operating parameters of quenching, i.e., the temperature after quenching and the quenching rate, were studied in detail and optimized after the kinetics were validated. The simulation results also proved that hydrogen can promote the formation of ethylene and inhibit the condensation of acetylene during quenching. In particular, in-depth discussion of acetylene decomposition and ethylene formation using this detailed kinetic mechanism combined with thermodynamic method provided a comprehensive understanding of the thermodynamics and kinetics interpreting pilot plant experimental data. - Highlights: • A detailed kinetic model for C_2H_2 decomposition and soot formation is established. • Two key operating parameters of quenching are studied in detail and optimized. • Effects of H_2 on C_2H_4 formation and C_2H_2 condensation during quenching are discussed. • A comprehensive understanding of the pilot plant experimental data is achieved.
[en] Varying thicknesses of the HfO2 films prepared by atomic layer deposition (ALD) were compared in terms of electrical properties and reliability. Scaling the physical thickness of the HfO2 dielectric did not increase the capacitance as expected due to the thicker interfacial SiOX layer obtained by the oxidation process used for thermal annealing. After thermal annealing, HfO2 crystallization increased with the thickness of HfO2 film, which then increases the dielectric constant for the bulk HfO2 film. The breakdown behaviors of the HfO2 gate dielectric film were not scaled to thickness, improved with HfO2 thickness until saturation. The reliability characteristics of the HfO2 dielectric under unipolar AC stressing were also evaluated. Dielectric breakdown failure time of unipolar AC stressing becomes longer in comparison to that stressed in constant voltage stress. As the thickness of the HfO2 dielectric increases, a larger lifetime enhancement is detected due to the effective charge de-trapping for thicker dielectrics under AC stressing. - Highlights: ► Thickness effects of HfO2 films on electrical properties and reliabilityare studied.► HfO2 crystallization and dielectric constant increased with HfO2 thickness.► Breakdown behaviors of HfO2 gate dielectric film improved with HfO2 thickness.► A larger lifetime enhancement for thicker dielectrics under AC stressing
[en] Introduction: N,N-dimethyl-2-(2-amino-4-["1"8F]fluorophenylthio)benzylamine (4-["1"8F]-ADAM, 2) is a potent serotonin transporter (SERT) imaging agent. In order to fulfill the demand of clinical studies, we have developed a fully automated one-pot two-step synthesis of this potent SERT imaging agent. Methods: The 4-["1"8F]-ADAM (2) was synthesized using a commercially available GE TRACERlab FN module. Briefly, the precursor, N,N-dimethyl-2-(2,4-dinitrophenylthio) benzylamine (1) in DMSO was reacted with K["1"8F]/K_2_._2_._2 in a glassy carbon reaction vessel at 120 °C for 7.5 min followed by reduction of the intermediate with NaBH_4/Cu(OAc)_2 in EtOH in the same vessel at 80 °C for 20 min. The reaction mixture was then purified with high-performance liquid chromatography (HPLC) and solid phase extraction (SPE) to give (2). The quality of (2) synthesized by this method was verified by HPLC and TLC as compared to its authentic sample synthesized by two-pot two-step method. Results: Using this automated one-pot two-step method, the radiochemical yield (RCY) of (2) was 2.5±0.8% (n=12, EOS) in a synthesis time of 100±6 min from EOB with a specific activity of 4.4±1.9 Ci/μmol (n=12, EOS). Radioligand (2) was stable over 4 h at room temperature. Conclusions: This fully automated one-pot two-step synthetic method using a commercially available GE TRACERlab FN module could simplify the synthesis of 4-["1"8F]-ADAM (2) and fulfill its demand for both animal and human studies, especially for study sites without a cyclotron. - Highlights: • 4-["1"8F]-ADAM (2) was prepared by one-pot two step method with TRACERlab FN module. • The RCY (2) was ~3%, synthesis time was ~100 min and SA was ~5.0 Ci/μmol (EOS). • The concentration of EtOH, ACN and DMSO in (2) were 10, 0.04, 0.5%, respectively. • (2) prepared by this method is suitable for both animals and human studies.
[en] The degradation induced by oxygen (O_2) plasma irradiation to the various low dielectric constant materials (low-k; k = 3.0–2.5) has been investigated in this study. The dielectric constant was observed to increase upon O_2 plasma treatment due to carbon atom depletion and Si-OH bond formation, which is strongly influenced by the bonding structure or strength of the low-k materials, and less related to the porosity. Moreover, the O_2 damage can be suppressed by densifying the low-k film's surface induced by He/H_2 remote plasma treatment. Additionally, the role of ions, photons, and radicals in the plasma in inducing the low-k material degradation was clarified by using a special designed structure. The experimental results showed that all components in the plasma have contributions in degrading the electrical and reliability performance of low-k film. Moreover, the synergy between the radicals, the photons, and the ions enhanced the damage. - Highlights: • Effect of O_2 plasma irradiation on the various low-k films • Role of ions, radicals, and photons in inducing plasma damage to porous low-k films • O_2 plasma damage on low-k films can be suppressed by performing He/H_2 remote plasma treatment. • Synergy between the radicals, the photons, and the ions enhanced the damage
[en] Highlights: • Fe"0 NPs induced infertility risk in C. elegans. • A C.elegans-based probabilistic risk assessment model is developed. • In situ remediation-released Fe"0 NPs impair soil ecosystems health. - Abstract: There is considerable concern over the potential ecotoxicity to soil ecosystems posed by zero-valent iron nanoparticles (Fe"0 NPs) released from in situ environmental remediation. However, a lack of quantitative risk assessment has hampered the development of appropriate testing methods used in environmental applications. Here we present a novel, empirical approach to assess Fe"0 NPs-associated soil ecosystems health risk using the nematode Caenorhabditis elegans as a model organism. A Hill-based dose-response model describing the concentration–fertility inhibition relationships was constructed. A Weibull model was used to estimate thresholds as a guideline to protect C. elegans from infertility when exposed to waterborne or foodborne Fe"0 NPs. Finally, the risk metrics, exceedance risk (ER) and risk quotient (RQ) of Fe"0 NPs in various depths and distances from remediation sites can then be predicted. We showed that under 50% risk probability (ER = 0.5), upper soil layer had the highest infertility risk (95% confidence interval: 13.18–57.40%). The margins of safety and acceptable criteria for soil ecosystems health for using Fe"0 NPs in field scale applications were also recommended. Results showed that RQs are larger than 1 in all soil layers when setting a stricter threshold of ∼1.02 mg L"−"1 of Fe"0 NPs. This C. elegans biomarker-based risk model affords new insights into the links between widespread use of Fe"0 NPs and environmental risk assessment and offers potential environmental implications of metal-based NPs for in situ remediation.
[en] Full text: Objective: To investigate FOG brain uptake in patients with hypo- and subclinical hyperthyroidism undergoing whole-body FOG PET/CT. Methods: Sixty-four patients who had received total thyroidectomy for thyroid carcinoma underwent whole-body FDG PETI CT. Thirty-two of them received imaging in subclinical hyperthyroid status (15 males; 17 females; mean age, 55 ± 14 years) while the other 32 age-matched patients underwent the scan 4 wk after thyroid hormone withdrawal (12 males; 20 females; mean age, 56 ± 13 years). Brain images were performed I h after 370 MBq intravenous injection using a dedicated PET/CT (Siemens Biograph BGO duo). FOG-uptake was quantified by the standardized uptake value (SUY), normalized to patient's body weight. The volume of brain was determined by PET with 40% maximum SUY threshold. The brain mean SUV (SUY mean) were calculated in each patient. Data were compared between the two groups. Results: The brain mean SUYs for the hypothyroid patients ranged between 3.11 and 6.35 (averaged SUY mean 5.13 ± 0.91) while those of the subclinical hyperthyroid patients varied from 3.53 to 8.29 (mean SUY mean 5.77 ± 1.04). There was a significant global reduction of brain FDG uptake in the hypothyroid group (II.] %, P < 0.0 I) but no significant changes in the sub-clinical hyperthyroid group compared to the controls. Conclusion: FDG brain uptake in subclinical hyperthyroid patients was significantly greater than that of patients with hypothyroidism, suggesting effects of thyroid hormone on cerebral glucose metabolism.
[en] It introduces an interface between radiation monitoring network based on CAN bus and Ethernet. The system used GM pipe to detect γ ray, employed LPC2294 as the core processor. As the main control chip, Ethernet controller DM9000 constructs hardware circuit between Ethernet and multi-CAN gateway. It transmitted the data detected by CAN but to the main control center through Ethernet for the total display of data and diagrams. (authors)
[en] A class of matrices, called -radial matrices (1-radial matrices) whose spectral radius equals their -norm (1-norm), is proposed in this paper and some theoretical results are established to give several necessary and sufficient conditions of this class of matrices. Then, some properties of this class of matrices are presented. Finally, some applications of this class of matrices in the linear discrete dynamic systems are studied such that the zero solution of the linear discrete dynamic systems is asymptotically stable.