722 research outputs found
Search for single vector-like quark production in hadronic final states at the LHC
No full textIn this paper, we study the discovery potential of a Vector-Like quark (VLB) via the process at the Large Hadron Collider (LHC) with TeV. In the framework of a simplified model, we perform a scan over its parameter space and test its viability following a Monte Carlo analysis developed to include all production and decay dynamics. We use cut-and-count combined with Extreme Gradient Boosting (XGBoost) methods to classify the signal and background events in order to improve the efficiency of signal identification and background rejection. We find that this approach can reduce background events significantly while the signal retention rate is much higher than that of traditional methods, thereby improving the VLB discovery potential. We then calculate the exclusion and discovery capabilities for VLBs and find that the advantages of the cut-and-count plus XGBoost method especially lie in the high-mass region, i.e., m_B > 1500 \text{ GeV}. We finally obtain the following LHC results in terms of the coupling and chiral structure of a singlet heavy VLB interactions: (i) for =0.2 and with 3000 fb, the quark mass can be be excluded (discovered) up to 3000 GeV (2500 GeV); (ii) for =0.2 and with 3000 fb, the exclusion (discovery) region can reach up to 4750 GeV (4250 GeV)
Nickel-encapsulated carbon nanotubes modified boron doped diamond hybrid electrode for non-enzymatic glucose sensing
No full textA hybrid non-enzymatic glucose sensor made by incorporating boron doped diamond (BDD) film electrode with nickel (Ni)encapsulated carbon nanotubes (CNTs) were facilely fabricated. The CNTs were grown directly on BDD films in the presence of pre-sputtered Ni layer as a catalyst by hot-filament chemical vapor deposition. The morphology and composition of the hybrid structure were assessed by scanning electron microscopy and Raman spectroscopy. As Ni layer thickness increased, the CNTs were less covered on the surface and the length of CNTs increased. The Ni particles were encapsulated into a large number of CNTs. Electrochemical results indicated that this hybrid structure significantly improved the electrochemical performance of BDD due to the increased specific surface area and synergistic effect of Ni and CNTs. The optimized glucose sensor revealed two broad linear range of 1.25 μM - 0.49 mM and 0.49 mM- 6.79 mM, with a high sensitivity of 1642.20 μA mM−1 cm−2 (R2 = 0.9988) and 1374.4 μA mM−1 cm−2 (R2 = 0.9969) respectively. In addition, the hybrid electrode exhibited a low limit of detection which was 1.0 μM (S/N = 3), and good selectivity and stability.</p
On four-dimensional Einstein affine hyperspheres
No full text© 2016 Elsevier B.V. It is well-known that Vrancken–Li–Simon classified locally strongly convex affine hyperspheres in Rn+1 whose affine metric are of constant sectional curvatures, but on the other side it is still a difficult problem to classify n-dimensional locally strongly convex affine hyperspheres whose affine metrics are Einstein. In this paper, we have solved the problem in case n=4.sponsorship: The first author was supported by grants of NSFC-11371330 and the second author was supported by grants of NSFC-11271214 and NSFC-11671224. (NSFC-11371330, NSFC-11271214, NSFC-11671224)status: Publishe
A Monte Carlo calculation of the secondary electron emission in the backward direction from a SiO2 macro-capillary
No full textA Monte Carlo calculation of the secondary electron emission from a SiO2 macro-capillary in the backward direction induced by electron irradiation is presented with the aim to understand transmission guiding of a scanning electron beam through a borosilicate glass macro-capillary. The theoretical modeling of electron transport in SiO2 capillary incorporates the elastic, inelastic and phonon scatterings, resulting, respectively, from the interactions with nucleus, electrons and phonons. The influence on electron inelastic scattering by the insulator bandgap is also considered. In this work a simplified approach has been employed to deal with the charging of the internal wall of the capillary and it is found that at a glancing incident angle, the secondary electrons are mostly originated from the top surface
Long-term stability of Au nanoparticle-anchored porous boron-doped diamond hybrid electrode for enhanced dopamine detection
No full textA porous boron-doped diamond (pBDD) was made for immobilizing gold nanoparticles on BDD facets by a special process, wherein methods of magnetron sputtering and thermal catalytic treatment were utilized. Au nanoparticles are seated in the pores of pBDD facets and could be more stable during electrochemical tests. This hybrid structure significantly improved the electrochemical properties due to the introduction of Au nanoparticles and pores, which could increase the specific surface area. The cyclic voltammetry oxidation peak current of the Au/pBDD electrode decreased with an average daily loss of 0.02 μA and maintained approximately 90.1% of its initial value after detecting dopamine once per two days for 30 days, showing an excellent long-term electrochemical stability. In addition, the Au/pBDD electrode exhibited excellent sensitivity for the detection of DA, and the limit of detection was 0.06 μM in a linear concentration range of 0.1 μM–1 mM. This work indicates that the Au/pBDD is an appropriate material for detecting DA in a long-term tests.</p
Photocathode Design in Photo‐Assisted Li‐O2 Batteries: Status and Perspectives
No full textABSTRACT Li‐O2 batteries with an ultrahigh theoretical energy density of up to 3500 W·h/kg have drawn extensive attention as future energy storage technologies. However, large discharge/charge overpotentials (> 1 V) and unsatisfactory cycling performance are the main obstacles for practical applications. Recently, integrating photocatalysis into Li‐O2 batteries has emerged as a promising method to mitigate overpotentials, but the rational design of photocathodes with excellent photoelectrochemical activity and stability remains challenging. This review focuses on recent research progress on the reaction mechanisms in photo‐assisted Li‐O2 batteries and the development of photocathodes. We present several strategies for tailoring catalytic materials from the perspectives of material selection and its catalytic performance optimization, aiming to provide a fundamental understanding and insights into the design of efficient photocathodes. The key challenges in constructing high‐performance photocathodes and potential strategies were also discussed, offering insights for the development and application of efficient photocathodes in photo‐assisted Li‐O2 batteries
Dendrimer-Based Demulsifiers for Polymer Flooding Oil-in-Water Emulsions
No full textTwo polyamidoamine-based dendritic molecules, named here as benzyl-G3 and octyl-G3, were synthesized using H2NCH2CH2NRCH2CH2NH2 (where R is either rigid benzyl or flexible octyl hydrophobic tails that are linked to the central nitrogen atom). With consideration of factors, such as the settling time, demulsifier dosage, temperature, oil content, and kinds of surfactants, the synthesized molecules were systematically investigated as demulsifiers for breaking up polymer flooding oil-in water emulsions. In comparison to traditional G3 polyamidoamine, both benzyl-G3 and octyl-G3 exhibited better demulsification efficiencies with a dosage of 200 mg/L at a relatively low temperature (30 degrees C) in short periods of time (40 min) and reached 99.3 and 99.8% oil removal rates as they were added to the low oil-containing emulsion (1500 mg/L), respectively. A series of measurement methods were then adopted to explore the demulsification mechanism of the two demulsifiers. The interfacial tension and zeta potential measurements indicated that the high demulsification efficiency of the two dendrimers could be due to electrostatic charge neutralization. Moreover, the dendrimers and surfactants showed strong interactions according to the turbidity measurements, the results of which demonstrated that the hydrophobic tails located at the center of the dendrimers also influenced the demulsification efficiency.National Natural Science Foundation of China [21274004]SCI(E)ARTICLE55395-54013
Recent Advances on Radionuclide Labeled Hypoxia-Imaging Agents
No full textHypoxic tissue exists in most of the solid tumors and hypoxia is a common character of these tumors. The existence of hypoxic tissue in the tumor decreases the efficacy of radiotherapy and chemotherapy. Radiolabeled hypoxia markers have been developed to measure the hypoxic tissue together with non-invasive imaging techniques such as PET, SPECT, and PET/CT. This offers a convenient approach to delineate the tumor providing useful information for diagnosing cancer and guiding the treatment plan. Bioreducible organic compounds have been developed as the hypoxia markers to probe tissue hypoxia noninvasively because they can be reduced and metabolized under hypoxic conditions; form adducts with cell components, and thus be trapped in the hypoxic tissue. These compounds include nitroimidazoles and other redox-sensitive compounds such as BnAO and ATSM. Different radionuclides have been used to label these compounds such as technetium-99m, iodine-123, fluorine-18, copper-64, etc. In addition, to detect hypoxia with endogenous hypoxia markers such as carbonic anhydrase IX (CA IX) and hypoxia-inducible factor-1 (HIF-1), some radiolabeled tracers have also been developed. This article is an overview of the progress in this area in the past decade including the development of radiolabeled compounds for hypoxia detection and problems associated with the hypoxia marker development.Pharmacology & PharmacySCI(E)PubMed6REVIEW81084-10971
Simulation and Verification or Cu@Ag Core-shell Sintered Paste for Power Semiconductor Die-attach Applications
No full textWith the increasing application of wide bandgap materials such as silicon carbide and gallium nitride in power devices, the working temperature of power devices has been pushed further. Therefore, it brings higher requirements for packaging materials. Sintered silver is a widely accepted chip connection material. However, silver suffers from high prices and electromigration. Therefore, a novel sintered material based on silver-copper core-shell structured particles raises the attention of researchers to solve this deficiency. To accelerate the development of new materials and their related processes, a four-sphere model of the silver-coated copper structure is established in this paper. The mathematical relationship between the porosity and thermal conductivity of sintered body and the actual sintering process was preliminarily established through the calculation based on a series of FEM simulations. The model was further validated through experiments. The modeling method and conclusion are utilized for future process adjustment, which is of great significance to accelerate the development, application, and reliability of new packaging materials.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material
Joint Analysis and Reliability Test of Epoxy-Based Nano Silver Paste Under Different Pressure-Less Sintering Processes
No full textRecent years, the sintered silver paste was introduced and further developed for power electronics packaging due to low processing temperature and high working temperature. The pressure-less sintering technology reduces the stress damage caused by the pressure to the chip, improves reliability, and is widely applied in manufacturing. Currently, most existed studies are focused on alcohol-based sintered silver pastes while resins have been demonstrated to improve the bonding properties of solder joints. Hence, the performance and sintering mechanisms with epoxy-based silver paste need to be further explored. In this work, a methodology for multifactor investigation is settled on the epoxy-based silver paste to reveal the relationship between the strength and the different influence factors. We first analyzed the characteristics of commercialized epoxy-based silver paste samples, including silver content, silver particle size, organic composition, sample viscosity, and thermal conductivity. Samples were then prepared for shear tests and microstructure analysis under different pressure-less sintering temperatures, holding time, substrate surface, and chip size. Full factor analysis results were further discussed in detail for correlation. The influence factors were ranked from strong to weak as follows: sintering temperature, substrate surface, chip size, and holding time. Finally, a thermal cycling test was carried out for reliability analysis. Epoxy residues are one of the possible reasons, which result in shear strength decreasing exponentially.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and Material
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