海洋源蛋白酶产生菌筛选及酶学特性的初步研究

从海洋源鱿鱼中筛选高产蛋白酶菌株。通过检测蛋白酶产生水解圈结合蛋白酶活性测定的方法筛选高产蛋白酶菌株,采用PCR技术对筛选菌株进行16S rRNA鉴定,并构建目的菌株的系统发育树,同时研究粗蛋白酶的酶学特性。结果表明:筛选得到的10株产蛋白酶活力较高的菌株,经鉴定分别属于芽孢杆菌属(Bacillus sp.)、普罗威登斯菌属(Providencia sp.)和假单胞菌属(Pseudomonas sp.)。其中SW5菌株产酶活性最高达257.67±2.44 U/mL,为甲基营养型芽孢杆菌(Bacillus methylotrophicus)。该菌株所产粗蛋白酶的酶学特性研究发现,其最适pH为8.0,最适温度为40℃,终离子浓度为1 mmol/L时Mn2+、Ba2+和Ca2+对该蛋白酶活性有较高的激活作用,而Fe~(2+)和Zn~(2+)能明显抑制该蛋白酶活性。     

基于v-SVR和MVPSO算法的边坡位移反分析方法及其应用

 针对传统粒子群算法存在搜索空间有限、容易陷入局部最优点的缺陷,通过引入迁徙算子和自适应变异算子,提出基于粒子迁徙和变异的粒子群优化(MVPSO)算法。基准测试函数结果表明,改进的MVPSO算法较传统的粒子群优化算法在收敛效率上有大幅度提高,在处理非线性、多峰值的复杂优化问题中能快速地搜索,得到全局最优解。应用改进的MVPSO算法搜索最佳的支持向量机(v-SVR)模型参数,建立岩体力学参数与岩体位移之间的非线性支持向量机模型,提高v-SVR的预测精度和推广泛化性。然后,利用v-SVR模型的外推预测替代耗时的FLAC正向计算,利用改进的MVPSO算法搜索岩体力学参数的最优组合,提出v-SVR和MVPSO相结合的边坡位移反分析方法(v-SVR-MVPSO算法),与传统的BP-GA算法和v-SVR-GA算法相比,该算法在反演精度和反演效率上均有较大幅度提高。最后,将本文发展的v-SVR-MVPSO算法应用到大岗山水电站右岸边坡岩体参数反演分析,并对边坡后续开挖位移和稳定性进行预测,取得较好的效果。     

宁波海产品中多氯联苯的残留与风险评估

为探讨多氯联苯(PCBs)污染物在宁波市售海产品中的组成规律及季节变化特征,按不同季节采集10种宁波居民主要食用海产鱼类,采用气相色谱法检测其中7种指示性多氯联苯残留量,并进行人体健康风险评价。结果表明,PCBs的残留质量分数为0.06~3.98μg/kg,其中PCB-52和PCB-153为主要组分。PCBs含量分布特征为秋季最高,冬季次之,夏季最低。宁波市售海产品中多氯联苯残留量水平在可接受的范围内。食用上层鱼的健康风险CV值小于食用下层鱼,PCBs监测是风险评估需要控制的关键因素。     

临氢设备用14Cr1MoR钢板的研制

本文详细地介绍了临氢设备用１４Ｃｒ１ＭｏＲ钢特厚板的性能研究。综合性能研究结果表明：研制的１４Ｃｒ１ＭｏＲ钢成分均匀，钢质纯净，夹杂物少；钢板各部位性能均匀，各向异性小，并具有良好的抗层状撕裂性能和具有良好的抗回火脆化能力；组织致密，综合性能优良。钢板各项性能远远超过研制技术条件的要求，达到或接近国外进口钢板实物水平。证明采用电弧炉＋ＬＦ／ＶＤ精炼＋４２００ｍｍ轧机轧制＋正火（加速冷却）＋回火工艺     

压力容器用12Cr2Mo1R钢板的研制

本文介绍了12Cr2MolR钢板的生产工艺和性能,详细地研究了钢板热处理工艺与组织及性能的关系,钢板在较宽的回火参数范围内均能得到良好的性能。对12Cr2MolR钢板的抗层状撕裂性能和抗回火脆化能力的研究证实均能满足临氢设备用2.25Cr-1Mo钢板的技术要求。     

Closed-Form Error Analysis of AF-CARQ with CSI-Assisted Relay over Nakagami-m Fading Channels

This paper presents a new Amplify-and-Forward Cooperative Automatic Repeat reQuest protocol with channel state information-assisted relay which is more suitable for the only-read access networks. The channels of any pair of terminations are quasi static flat Nakagami- \(m\) fading channels, which are mutually independent and non-identically distributed. Assuming that the coherent equal gain combining is adopted to combine the retransmitted signals from the same link at the destination and selective combining is adopted to the signals from different links. Based on the approximation of product of Nakagami- \(m\) variables, we obtain the end-to-end signal-to-noise rate of any link. The closed-form expression of the average bit error rate for several modulation schemes is obtained by analyzing cumulative distribution function (CDF) and Gaussian Q-function. Then we analyze the amount of fading of the fading channels by the \(n\) order moment which is obtained by CDF. Numerical simulation results show that the relay node can resist the fading of system effectively comparing with the system without relay node. And with the increasing of the number of transmission, the performance advantage of relay link is more and more obviously. It is better to let the maximum transmission time \(F=6\) , which is very useful for improving the transmission efficiency of the truncated ARQ system. The maximum reduction of amount of fading can be reached when \(t=3\) , if the total number of transmission is \(f=6\) . The number of bits in the frame should not have too big.     

乳酸菌高抗氧化活性菌株的筛选及鉴定

乳酸菌的抗氧化性已得到体内体外试验的证实。从4种食物样品中初步筛选得到20株乳酸菌菌株。以VC作阳性对照,超氧阴离子自由基清除率及抗脂质过氧化率为指标复筛,得到2株优良菌株H15和H17;经16S rDNA序列分析鉴定及鼠李糖发酵试验,得出H15为戊糖乳杆菌(Lactobacillus pentosus),H17为植物乳杆菌(Lactobacillus plantarum)。通过乳酸菌菌悬液及无细胞提取物的抗氧化性能比较研究,推测出乳酸菌的抗氧化性能是因其不同且相对独立的抗氧化机制所致;乳酸菌菌体表面的某些成分同样具有一定的抗氧化性,然而这些物质的抗氧化性能随菌体及自由基的不同而不同。     

乙醇再生微晶纤维素的分级及其结构表征

在微晶纤维素（MCC）的Na OH/尿素溶液中加入不同质量的无水乙醇进行分级沉降，得到分级再生微晶纤维素。通过黏度法测定了再生微晶纤维素的聚合度，采用FTIR、XRD、XPS、TG和SEM对再生微晶纤维素的结构、结晶度、热稳定性和形貌进行了表征。结果表明，随着分级次数的增加，再生微晶纤维素的聚合度逐渐降低，3次分级后微晶纤维素的聚合度由MCC的203降至77；微晶纤维素形貌由表面光滑的棒状纤维结构变为粗糙多孔的结构；再生微晶纤维素的晶型由MCC的Ⅰ型转变为Ⅱ型，3次分级后微晶纤维素的结晶度由MCC的65.58%降至32.05%。分级再生微晶纤维素的自由羟基增加，参与成键的羟基减少；再生微晶纤维素的热稳定性随着分级次数的增加而降低，3次分级后初始分解温度由MCC的310℃降至257℃。     

Dietary flavonoids: a novel strategy for the amelioration of cognitive impairment through intestinal microbiota

The chances of people suffering from cognitive impairments increase gradually with age. Diet and lifestyle are closely related to the occurrence and development of cognitive function. Dietary flavonoid supplementation has been shown to be one of the protective factors against cognitive decline. Flavonoids belong to a class of polyphenols that have been proposed for the treatment of cognitive decline. Recent evidence has shown that intestinal flora in the human body can interact with flavonoids. Intestinal microbiota can modify the chemical structure of flavonoids, producing new metabolites, the pharmacological activities of which may be different from those of the parent; meanwhile, flavonoids and their metabolites can, in turn, regulate the composition and structure of intestinal flora. Notably, intestinal flora affect host nervous system activity through the gut-brain axis, ultimately causing changes in cognitive function. This review therefore summarizes the interaction of dietary flavonoids and intestinal flora, and their protective effect against cognitive decline through the gut-brain axis, indicating that dietary flavonoids may ameliorate cognitive impairment through their interaction with intestinal microbiota. © 2022 Society of Chemical Industry.