Cryoprotection in electron microscopy

A set of experiments has been undertaken to resolve questions about the cryoprotection factor afforded by cooling specimens in the electron microscope. Two specimens, an n-alkane (paraffin) and bacterial purple membrane, were prepared and distributed to several laboratories. Radiation damage studies were carried out at these laboratories independently, but following a standard protocol as closely as possible. While it was not possible to make all measurements at all of the laboratories, sufficient data have been obtained to establish a general reproducibility in the overall features of the cryoprotection effect from room temperature to near 4.2 K.     

亚热带农业小流域暴雨过程硝态氮迁移特征及水文示踪研究

为揭示亚热带丘陵区农业小流域暴雨过程中硝态氮迁移规律及其主要水文输送途径,本研究通过对紫色土丘陵区典型农业小流域典型暴雨过程跨尺度(从3~1 236 hm2)连续监测,分析径流硝态氮迁移动态特征及其尺度效应,并对比δ18O和硝态氮作为示踪剂的端元混合分析(EMMA)解析结果,探讨硝态氮作为暴雨过程水文示踪剂的可行性。结果表明:(1)两场暴雨事件中源头小流域苏荣小流域(含集镇污水)径流中硝态氮浓度最高,而到达梯级小流域出口处(万安小流域)硝态氮浓度最低,林地来水的贡献是较大尺度小流域径流硝态氮浓度降低的主要原因,坡耕地壤中流补给可能是径流消退过程中硝态氮出现浓度峰值的主要原因。(2)EMMA模型解析结果显示:δ18O与硝态氮均能示踪农业小流域径流消退期间壤中流补给过程;但硝态氮在受人居活动强烈影响子流域的示踪应用需谨慎。以农业为主的亚热带丘陵区小流域中,硝态氮具有同时作为环境效应指示剂和水文示踪剂的潜力,但其应用效果仍有待于进一步验证。     

茶树芽叶花色苷含量测定方法的研究

茶树芽叶中的花色苷含量测定尚无国家标准,目前仍沿用单一pH法进行测定.比较了单一pH法和pH示差法对花色苷含量测定的结果.单一pH法所测花色苷含量高于pH示差法,两者存在良好的线性关系（R2=0.992 7）.pH示差法能较好地消除干扰物质对测定结果的影响,为茶叶的花色苷定量分析提供了依据.     

The morphology and structure of crystals in Qing Dynasty purple‐gold glaze excavated from the Forbidden City

Ancient Chinese purple‐gold glaze (zijinyou) is popular for its beautiful figuration, unique allure and fine craftsmanship. To understand the crystalline nature in the purple‐gold glaze, the morphology and structure of crystals precipitated in the glaze layer of purple‐gold glaze porcelain fired during the Qing Dynasty were characterized by a variety of methods combining X‐ray and electron‐based techniques. A large quantity of single‐phase twinning ε‐Fe₂O₃ crystals with lengths of 1‐3 μm, widths of less than 1 μm, and thickness of approximately 150 nm are found dispersed across the glaze surface to a depth of approximately tens of micrometers. These crystals show stratification across the cross‐section of the purple glaze consisting of 4 sublayers according to the crystal size. The formation of ε‐Fe₂O₃ crystals primarily contributed to the reddish‐brown tones of the purple‐gold glaze. The presence of anorthite, a strong reducing atmosphere during the firing process and the vitreous nature of the glaze influenced the growth of ε‐Fe₂O₃ crystals. These results suggest the controllability of single‐phase ε‐Fe₂O₃ crystals by identifying and understanding the underlying chemical processes in ancient Chinese crystalline glaze porcelain, and the findings will provide insights for modern material scientists in preparing ε‐Fe₂O₃ crystals with large sizes and high purities.     

响应面法优化甘薯脆片干燥工艺

为探究甘薯脆片热泵干燥最佳工艺,在单因素试验基础上,以烘干温度、烘干时间、切片厚度、汽漂时间为影响因素,以含油率及感官评分为响应值,用Box-Behnken试验设计建立响应面分析模型。结果表明,甘薯脆片烘干最佳工艺为:烘干温度74℃、切片厚度2.7 mm、汽漂时间3 min,烘干时间为3.5 h,在此优化条件下,甘薯脆片油炸后感官评分为88.75分,含油率为7.84%,在此条件下得到的产品色香味俱全。     

不同氧含量的氧化钨粉对超细钨粉制备的影响

研究了不同氧含量的氧化钨粉对超细钨粉制备的影响。结果表明,以蓝钨(WO_(2.90))为原料制取的钨粉粒度都在1μm左右,以紫钨(WO_(2.72))为原料制备的钨粉的粒度均小于以蓝钨为原材料制备的粉体。不同氧含量的氧化钨粉制备超细钨粉时,影响粉末FSSS粒度的顺序为:还原温度氢气流量装舟量推舟速度。以紫钨为原料,在还原温度700~840℃、推舟速度18min/舟、装舟量0.35kg/舟、氢气流量50~60m3/h的条件下,制备的钨粉粒度为0.3μm左右。     

紫薯熟全粉变温压差膨化干燥技术研究

采用紫薯为原料,以紫薯熟全粉的彩度指数b*值、花青素含量、碘蓝值为评价指标,探讨了膨化温度、停滞时间、抽空温度等变温压差膨化干燥因素对各评价指标的影响,运用响应面法中Box-Behnken试验设计确定了变温压差膨化干燥工艺参数：膨化温度90 ℃、停滞时间7 min、抽空温度70 ℃,结果表明：该条件下制得的紫薯熟全粉彩度指数b*值可达-6.573、花青素含量达1.51%、碘蓝值为19.06,产品为紫红色,花青素含量及紫薯气味都保留较好。     

紫薯花青素提取条件优化及淀粉等产物的制备

以‘紫罗兰’紫薯为原料,研究同步提取紫薯花青素以及制备紫薯淀粉、纤维素和紫薯蛋白的工艺及参数。紫薯与酸乙醇（pH 2）混合破碎、过滤、沉淀分离淀粉;将滤渣和分离淀粉后上清液混合,用微波辅助法提取花青素并优化提取条件;花青素提取液沉淀分离紫薯蛋白;提取花青素的滤渣制备紫薯纤维素。结果表明：微波辅助提取紫薯中花青素的最佳工艺条件为微波时间4 min、微波温度52 ℃、料液比1∶22.40（g/mL）、乙醇体积分数62%（pH 2）,在此条件下紫薯花青素的提取率（93.64±0.69）%、粗提物中花青素含量（9.58±0.20） mg/g。制备的紫薯淀粉质量分数（95.77±0.41）%、得率（占总淀粉质量分数）（73.06±1.03）%;滤渣粉中纤维素含量（117.11±2.69） mg/g;制备的紫薯蛋白中蛋白质含量（524.78±24.84） mg/g。该制备方法能够提高紫薯的利用率,降低生产成本。     

紫薯花色苷的理化性质研究

对紫薯花色苷的理化性质进行了研究,结果表明,其在中性偏酸的条件下呈现鲜艳的红色或悦目的紫色;对H_2O_2、Na_2SO_3以及光线表现出不稳定性;水溶液具有色泽或者氧化还原性的金属离子也会影响其色泽;具有良好的热稳定性;对于常用的食品添加剂如蔗糖、NaCl、防腐剂等具有良好的配伍稳定性;具备良好的贮藏稳定性,常温避光的情况下能放置5个月无明显变化,紫薯花色苷是优良的天然色素来源.