An Effective Method of SNR Estimation for LDPC-CPM

The technique of SNR estimation is one of the key technologies in adaptive frequency hopping system. The methods of channel quality estimation for non-linear continuous phase modulation (CPM) signals have some limitations. Therefore, the algorithm of channel quality estimation for CPM signals is worthy of further study. Some similar phase characteristics between sampling CPM and MPSK motivate us to propose a channel estimation algorithm with applications to nonlinear CPM using linear modulation signal processing. A comprehensive analysis of LDPC-CPM schemes using proposed algorithm is presented, and simulation results indicate that the proposed method can not only estimate channel quality well but also make the normalized MSE (NMSE) of SNR estimate close to/less than 0.1 dB at SNR of 4 dB using short block codes. It shows that the algorithm in this paper is effective enough to estimate the signal to noise ratio (SNR). Meanwhile, the algorithm in this paper reduces the complexity of computation compared with other traditional algorithms.

The underappreciated role of fugitive VOCs in ozone formation and health risk assessment emitted from seven typical industries in China

Fugitive emission from industrial sources may result in ozone formation and health risk,while the exact contribution of this source remains incompletely understood.In this study,emission characteristics,ozone formation potential(OFP)and health risk of fugitive VOCs in7 representative industries were investigated.Chemical material industry was the dominant contributor to VOCs of fugitive emission in comparison with other industries.The OFP of VOCs from fugitive emission was in the range of 1.45×10^(3)-3.98×10^(5)μg/m^(3),with a higher value than that of organized emission in seven industries except for the coking industry and the chemical material industry,suggesting that fugitive VOCs should be taken into account while developing control strategies.Acetaldehyde,m,p-xylene,n-nonane,ethylene,vinyl chloridethe and other high OFP-contributing species were the major reactive species that should be targeted.Health risk assessment investigated non-cancer and cancer risks of fugitive VOCs in 7 industries were all above safe level(HR>1 and LCR>1×10^(-4)),posing remarkable health threats to human health.OVOCs were the main contributor to non-cancer risk,while halohydrocarbons and aromatics contributed most to cancer risks,posing remarkable health threat on human health.Our findings highlighted the contribution of fugitive VOCs on ozone formation and health risk was underestimated,indicating which should be considered in emission control strategies of industrial sources.

Expression of phenylalanine ammonia lyase as an intracellularly free and extracellularly cell surface-immobilized enzyme on a gut microbe as a live biotherapeutic for phenylketonuria

Phenylketonuria(PKU),a disease resulting in the disability to degrade phenylalanine(Phe)is an inborn error with a 1 in 10,000 morbidity rate on average around the world which leads to neurotoxicity.As an potential alternative to a protein-restricted diet,oral intake of engineered probiotics degrading Phe inside the body is a promising treatment,currently at clinical stage II(Isabella,et al.,2018).However,limited transmembrane transport of Phe is a bottleneck to further improvement of the probiotic’s activity.Here,we achieved simultaneous degradation of Phe both intracellularly and extracellularly by expressing genes encoding the Phe-metabolizing enzyme phenylalanine ammonia lyase(PAL)as an intracellularly free and a cell surface-immobilized enzyme in Escherichia coli Nissle 1917(EcN)which overcomes the transportation problem.The metabolic engineering strategy was also combined with strengthening of Phe transportation,transportation of PAL-catalyzed trans-cinnamic acid and fixation of released ammonia.Administration of our final synthetic strain TYS8500 with PAL both displayed on the cell surface and expressed inside the cell to the Pah^(F263S)PKU mouse model reduced blood Phe concentration by 44.4%compared to the control Ec N,independent of dietary protein intake.TYS8500 shows great potential in future applications for PKU therapy.

Fine-tuning Bacterial Cyclic di-AMP Production for Durable Antitumor Effects Through the Activation of the STING Pathway

The stimulator of interferon genes(STING)protein is an important and promising innate immune target for tumor therapy.However,the instability of the agonists of STING and their tendency to cause systemic immune activation is a hurdle.The STING activator,cyclic di-adenosine monophosphate(CDA),produced by the modified Escherichia coli Nissle 1917,shows high antitumor activity and effectively reduces the systemic effects of the“off-target”caused by the activation of the STING pathway.In this study,we used synthetic biological approaches to optimize the translation levels of the diadenylate cyclase that catalyzes CDA synthesis in vitro.We developed 2 engineered strains,CIBT4523 and CIBT4712,for producing high levels of CDA while keeping their concentrations within a range that did not compromise the growth.Although CIBT4712 exhibited stronger induction of the STING pathway corresponding to in vitro CDA levels,it had lower antitumor activity than CIBT4523 in an allograft tumor model,which might be related to the stability of the surviving bacteria in the tumor tissue.CIBT4523 exhibited complete tumor regression,prolonged survival of mice,and rejection of rechallenged tumors,thus,offering new possibilities for more effective tumor therapy.We showed that the appropriate production of CDA in engineered bacterial strains is essential for balancing antitumor efficacy and self-toxicity.

耐甲氧西林金黄色葡萄球菌MRSA252辅酶A二硫化物还原酶缺失延缓苯唑西林的次级损伤效应

【目的】耐甲氧西林金黄色葡萄球菌在苯唑西林作用下,其辅酶A二硫化物还原酶表达上调2.3倍。本文研究苯唑西林对该酶缺失的金黄色葡萄球菌的杀菌效应。【方法】利用同源重组双交换技术对金黄色葡萄球菌进行基因敲除,并用质粒p OS1构建回补株;采用分光光度法检测菌株体外增殖能力;以时间-杀菌法考察苯唑西林对菌株杀菌效应;以2’,7’-二氯荧光黄双乙酸盐为探针检测胞内活性氧水平。【结果】辅酶A二硫化物还原酶基因敲除株较亲株生长缓慢(P<0.05);20倍MIC浓度苯唑西林下敲除株的时间-杀菌曲线及胞内活性氧水平与亲株无显著性差异,5倍MIC浓度下敲除株的致死速率及胞内活性氧水平均较亲株下降。【结论】在较低浓度苯唑西林作用下,辅酶A二硫化物还原酶基因缺失降低胞内活性氧水平,减小杀菌速率,延缓次级损伤效应。

Microstructure Evolution and Tensile Properties of Ti_3Al/Ni-based Superalloy Welded Joint

In the present work, the dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy was attempted by gas tungsten arc （GTA） welding technology. Sound joints were successfully achieved by using a Cu-Ni alloy as filler material. According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti3Al interface were verified as follows： Ti2AlNb phase dissolved with Cu and Ni; Al（Cu,Ni）2Ti, （Cu,Ni）2Ti and （Nb, Ti） solid solution; Cu-rich phase and a complex multi-element phase. The In718/weld interface is characterized by solid solutions of Ni, Cu, Cr, Fe and Nb. The average tensile strength of the as-welded joints at room temperature is 163 MPa, and after a post-weld heat treatment it is increased slightly to 177 MPa. The fracture occurred at the surfacial layer of the joined Ti3Al base alloy, indicating that the Ti2AINb layer dissolved with Cu and Ni is the weak link of the Ti3Al/In718 joint.