EESM中最佳β值的确定

研究EESM中最佳β值的确定算法。首先根据MMSE准则建立确定最佳β值的数学模型,然后根据均方误差函数的下凸性给出确定最佳β值的迭代算法。数值仿真结果表明,随着迭代次数的增加,所提算法均方误差整体趋势是下降的,算法获得的最佳β值对应的BLER-SINR曲线与AWGN信道下BLER-SINR曲线在很大范围内是接近的。     

二氧化硅／聚甲基丙烯酸-β-羟乙酯合成及表征

采用溶胶-凝胶法,以正硅酸乙酯为无机先驱体、盐酸为催化剂合成二氧化硅（SiO2）溶胶;以过硫酸钾（K2S2O8）为引发剂,将SiO2溶胶与甲基丙烯酸-β-羟乙酯（HEMA）反应合成SiO2/聚甲基丙烯酸-β-羟乙酯（PHE—MA）凝胶。讨论了温度、无水乙醇和稀盐酸的体积比、K2S2O8和HEMA的用量对溶胶-凝胶的影响。用傅里叶变换红外光谱仪和差热分析仪对SiO2／PHEMA凝胶进行了表征。研究表明：温度越高．溶胶-凝胶时间越短：无水乙醇和稀盐酸体积比为2时,溶胶时间最短;增大HEMA、K2S2O8用量,加速凝胶形成;SiO2／PHEMA为杂化材料,其耐热性高于PHEMA．     

Change in anthocyanin concentrations in red apricot fruits during ripening

Here we report on accumulation patterns of anthocyanins and of β-carotene during fruit maturation, between 82 and 125 days after flowering, of two apricot (Prunus armeniaca L.) cultivars, A3576 and A3751. Both cultivars displayed an intense red colour of the skin but differed in their genetic background. The pigments were extracted from skin and flesh, separately, and analysed using HPLC-DAD-MS. Out of three anthocyanins detected here, the major compound, cyanidin-3-O-rutinoside was present at 75%. The two minor compounds were cyanidin-3-O-glucoside and peonidin-3-O-rutinoside. This is the first time that peonidin-3-O-rutinoside has been detected in apricot fruit. During maturation, A3751 accumulated anthocyanins in both skin and flesh, whereas anthocyanins were present only in the skin of A3576. The skin anthocyanin content was higher in A3751 (296 mg kg⁻¹) than in A3576 (41 mg kg⁻¹). Maximum anthocyanin levels were attained after 108 and 118 days of flowering in A3751 and A3576, respectively, in conjunction with loss of firmness and red colour acquisition on the un-blushed side of the fruit. At the end of ripening, the β-carotene flesh concentration reached 5 mg kg⁻¹ in A3576 and 15 mg kg⁻¹ in A3751. A significant effect of environment was observed on the anthocyanin content in the two cultivars.     

东方Cheese发酵过程中异黄酮、苷元及组分的研究

东方Cheese经毛霉发酵能去除某些过敏源,这种无盐制品深受日本民众欢迎。文中通过正交试验优化了东方Cheese中异黄酮的提取条件。采用了三波长二标样法和HPLC测定异黄酮含量和组成。检测了东方Cheese发酵过程中异黄酮含量及组成的变化:异黄酮的总量降低了37.90%;其中糖苷由34.02μg/mL降至3.11μg/mL(即已有90.86%糖苷转化为苷元),苷元含量则相应的由0.97μg/mL升至18.62μg/mL。认为异黄酮总量降低以及组成变化的主要因素是糖苷到苷元分子质量的降低和样品含水量提高;发酵后期限制组成变化的主要因素是底物浓度的降低。     

Dissolution tests as a tool for predicting bioaccessibility of nutrients during digestion

Bioaccessibility and bioavailability of active ingredients (like vitamins, antioxidants, etc.) into food systems is often compromised by factors like low permeability and/or solubility within the gut, lack of stability during food processing (temperature and oxygen) as well as in the gastrointestinal tract (pH, enzymes, presence of other nutrients). Moreover, little is known on the influence of food structure and breakdown in the gut on nutrient release. The possibility of predicting the release of nutrients from food matrices under simulated gastrointestinal conditions is of great relevance in order to define which food matrix is best for which nutrient, as well as for looking at the interaction of ingredients with the enzymes involved in the digestive process. This study explores the potential relevance of dissolution tests as a tool for predicting bioaccessibility of nutrients during in vitro digestion. Whey protein hydrogels containing green tea extract (GTE) were chosen for this study. Different simulated in vitro gastrointestinal conditions (GI) were applied throughout the dissolution experiments and the GTE was analysed by UV–vis absorption spectroscopy. It was possible to distinguish between two different release kinetics when experiments were performed in simulated gastric or intestinal media. In the gastric step, the kinetic of GTE release was lower than in an intestinal environment, suggesting that more GTE is released and available for absorption into the intestine than in the stomach. The present study shows that it is possible to use the dissolution tester as a screening method to mimic nutrient release from a food matrix in the gastrointestinal tract.     

Antioxidant activity and phenolic content of phenolic rich fractions obtained from black cumin (Nigella sativa) seedcake

The antioxidant activities of crude methanolic extract (CME) and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black cumin seedcake were investigated. DPPH radical scavenging activity, β-carotene–linoleate bleaching, and inhibition of corn oil oxidation were used to evaluate the antioxidant capacity. The total phenolics were found to be 78.8, 27.8, 32.1 and 12.1 mg gallic acid equivalents (GAE)/g in EAF, CME, WF and HF, respectively. The CME and EAF exhibited the highest DPPH followed by WF and HF. The extract/fractions showed high effect on reducing the oxidation of β-carotene. The effect of extract/fractions on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The oil peroxide and anisidine values were generally lower with addition of PRFs in comparison to a control. The predominant phenolic compounds identified by HPLC–DAD in CME and WF of black cumin seedcake were hydroxybenzoic, syringic and p-cumaric acids.     

Characterization of Aspergillus oryzae glycoside hydrolase family 43 β-xylosidase expressed in Escherichia coli

This is the first report of glycoside hydrolase family 43 β-xylosidase from Aspergillus oryzae. To characterize this enzyme, the recombinant enzyme was expressed in Escherichia coli. Unlike known β-xylosidases from fungal origins, the enzyme did not show substrate ambiguity and was stable at alkaline pH.     

液相色谱-串联质谱法测定牛奶中舒巴坦和他唑巴坦

A triple quadrupole liquid chromatography tandem mass spectrometry method is presented for the quantitative determination and confirmation of salbactam and tazobactam, the inhibitors of β-lactamase in milk. Milk was extracted with methanol, and the extracts were analyzed by LC-MS/MS in negative mode. The LOQs of salbactam and tazobactam in milk are 10 μg•L^－1 and 100 μg•L^－1, respectively.     

Cefuroxime-impregnated calcium phosphates as an implantable delivery system in experimental osteomyelitis

The study aimed to investigate the effectiveness of porous calcium phosphates viz., hydroxyapatite (HAp) and a bi-phasic calcium phosphate (BCP) with predominately β-tricalcium phosphate (β-TCP) prepared by aqueous solution combustion method impregnated with cefuroxime axetil for the treatment of experimental osteomyelitis and compared with parenteral treatment. In vitro release of the drug was tested for its sustained elution characteristics for 21 days in PBS (pH 7.2) and measured by HPLC. In the in vivo study, bone infection was induced in tibia of rabbits by inoculation of 1 ml (3 × 10⁶) CFU Staphylococcus aureus. On the 21st day, after the development of osteomyelitis, six animals were treated by filling the cavity with cefuroxime-impregnated HAp blocks (Group II), six animals with the same drug-impregnated β-TCP (Group III) and in six others, only cefuroxime (15 mg/kg twice daily) was injected parenterally 6 weeks (Group IV). Group I with six animals was kept untreated. Histologically, the signs of infection were found to subside by 3 and 6 weeks. Radiological evaluation with cefuroxime-impregnated HAp and β-TCP pointed out the disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime in bone and serum as estimated by HPLC showed highest value on day 21 itself which reduced marginally by day 42 in both the groups and these values were higher than minimum inhibitory concentration (MIC) against S. aureus. Our findings suggest that bi-phasic calcium phosphates with predominately β-TCP content is a very efficient carrier material for antibiotic compounds even for refractory infections by S. aureus.     

氮-甲醇和吸热式渗碳气氛的应用和比较

本文对氮-甲醇和以C3H8为原料气制备的吸热式渗碳气氛在实际生产中的应用情况进行了分析和比较,结果证实氮-甲醇渗碳气氛渗碳速度更快。