The variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are more transmissible, with a reduced sensitivity to vaccines targeting the original virus strain. Therefore, developing an effective vaccine against both the original SARS-CoV-2 strain and its variants is an urgent need. It is known that the receptor-binding domain (RBD) in the S protein of SARS-CoV-2 is an important vaccine target, but subunit vaccines usually have lower immunogenicity and efficacy. Thus, selecting appropriate adjuvants to enhance the immunogenicity of protein-based subunit vaccine antigens is necessary. Here, an RBD-Fc subunit vaccine of SARS-CoV-2 has been generated, followed by vaccination in B6 mice, and four adjuvant regimens were investigated, including aluminum salts (Alum) + 3-O-desacyl-4′-monophosphoryl lipid A (MPL), AddaVax, QS21 + MPL, and Imiquimod. The adjuvant potency was evaluated by comparing the elicited polyclonal antibodies titers with measuring binding to RBD and S protein in ELISA and Western blot analysis, and also the cross-neutralizing antibodies titers using a pseudovirus infection assay of hACE2-expressing 293T cells, with pseudoviruses expressing the S protein of the SARS-CoV-2 original strain and Delta strain. The presence of QS21 + MPL adjuvant induced stronger polyclonal antibody response and neutralization potency blocking the original strain and Delta strain, as compared with the non-adjuvant RBD-Fc group and other adjuvant groups. Meanwhile, Imiquimod even had a negative effect in inducing specific antibodies and cross-neutralizing antibody production as an adjuvant.
A series of Ni and Ni-Co were maintained on a mixed support of USY (ultrastable Y) zeolite and active aluminum oxide. The catalysts were characterized by means of element analysis, BET and XRD. The characterization results suggested that the active metal components were introduced without changing the microstructure. Then catalytic hydrocracking activity was studied using AATO (distillate of coal tar) in a tubular reactor. AATO conversion was 39.40% and 41.37% using the 10%Ni/USY catalyst and 10%Ni-6%Co/USY catalyst, the hightest total selectivity of benzene and xylol was 67.1% in 10%Ni-10%Co/USY catalyst than others under the reaction conditions studied [T=480°C, P=4.5MPa, LHSV=3.0h-1].
This paper presents a novel method of field reliability prediction considering environment variation and product individual dispersion. Wiener diffusion process with drift was used for degradation modeling and a link function which presents degradation rate is introduced to model the impact of varied environment and individual dispersion. Gamma, transformed-Gamma (T-Gamma) and Normal distribution with different parameters are employed to model rightskewed, left-skewed and symmetric stress distribution in the study case. Results show obvious difference in reliability, failure intensity and failure rate compared to constant stress situation and each other. It indicates that properly modeled (proper distribution type and parameters) environmental stress is the fundamental of varied environment oriented reliability prediction. In a linear drift degradation process and Arrheniustype link function situation, it is reasonable not concerning about product individual dispersion because the impact is barely small, while other situations can be studied in the same way proposed in this present paper. I TRODUCTIOReliability testing is carried out to study how environmental conditions affect the product performance. But these tests are usually conducted at a certain virtual environmental stress level whereas the field environment is highly varied from the virtual environment. However, there is little understanding on how field environment affect product reliability. Most of previous works of field reliability prediction treat environment stress as a constant at the average level [1] and may fail to give accurate prediction when the field environment is given. Meeker and Escobar [2] proposed a general framework using laboratory test results to predict field performance in a highly varied environment. Eghbali [3] proposed a proportional degradation hazard model which was employed by Wang [4] to extend existing degradation model capabilities to field systems. Vaca-Trigo and Meeker [5] provided a statistical model for linking field and laboratory exposure results for a model coating. Meeker and Escobar[6] developed a model and method for combining accelerated test data and field data to predict the failure time distribution for a future improved product operating in the same environment conditions. However, these works cannot handle the situation that the environment can be modeled by a statistical distribution. Then Liu and Ma [7] proposed a method to conduct field reliability prediction, employing Wiener diffusion process with drift to model the degradation process and an Arrhenius-type link function with Gamma distribution to describe temperature variation.However, all these works did not discuss how the type and parameters of environment distribution affect reliability, failure intensity and failure rate. Moreover, each product has different degradation rate due to individual dispersion caused by random factors in material preparation and manufacturing process. It is also reasonable to be considered in reliability prediction.I...
By using heavy polycyclic aromatic hydrocarbon from a factory in Northwest China as raw material and 6% Ni/USY as catalyst, a study on hydrogenation process is carried out with a high-pressure hydrocracking assessment device, which mainly focuses on investigating the effect of LHSV, oil hydrogen ratio, temperature and pressure on heavy polycyclic aromatic hydrocarbon. Experimental results show that under the condition that the optimum LHSV is 3.0 h-1 and the ratio of oil to hydrogen is 600, both conversion rate of heavy components and yield of one-membered ring increase at first and then decrease with reaction temperature, with the peak value of conversion rate at 320°C and yield peak at 340°C. Though fluctuates with the increase of pressure, but conversion rate of heavy components shows an overall upward trend. Yield of one-membered ring increases at first and then decreases with pressure, and eventually tends to stabilize. When the temperature is greater than 300°C, the yield slightly fluctuates with pressure and shows an overall increasing trend.
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