Sunflower Head Residue Pectin Extraction as Affected by Physical Conditions

Effects of extraction pH, temperature, and time on yield and quality of pectin from sunflower heads (Interstate cultivar) were investigated. The low-methoxyl pectin was extracted, using 0.75% sodium hexametaphosphate at pH 3, 4, and 5 and at 75, 85, and 95°for 20, 40, and 60 min, respectively. Yield, molecular mass, and firmness of jellies of the pectins were determined. Three-way statistical analysis on yield, molecular mass and gel firmness showed strong interactions among pH, temperature and time. Highest yields were obtained at pH 5, 95°for 20 min and pH 4, 85°for 40 min. Pectin extracted for 40 min at pH 3 and 4 and at 85°and 75°C, respectively, had the highest molecular mass. Gel firmness of sunflower pectin prepared at pH 5.4 was higher than that of a commercial citrus pectin.     

Criterion for conditional stability of Ml MO integral control

A simple criterion to detect the conditional stability of MI MO systems with integral control is described, It is shown that a closed-loop system with a loop-transfer matrix H(s)/s is made unstable by undesirable feedback-gain reduction if any of the principal minors of [si - H(0)] have zeros in the left half-plane.     

燃料挥发性对柴油机性能及排放的影响

针对不同的发动机热状态及压缩比，试验研究了燃料物化特性对柴油机稳态及过渡工况下性能、排放的影响规律。应用自行开发的柴油机过渡工况控制系统及排气采集装置，模拟车用柴油机实际工作时的加速状态，对具有相同十六烷值但有不同挥发性能燃料的HC排放特性进行了研究，利用气相色谱仪对HC排放成分进行了分析。研究结果表明，采用挥发性好的燃料，可有效降低排气烟度，提高有效热效率，在发动机热状态不好及压缩比较低等燃烧条件恶劣、HC排放高的情况下，可有效地降低HC排放。     

放电等离子超快速烧结氧化铝力学性能和显微结构研究

本文介绍用和电等离子超快速烧结方法制备的氧化铝陶瓷的力学性能和显微结构特征，超快速烧结的升温速率为６００℃／ｍｉｎ，在烧结温度不保温，迅即在３ｍｉｎ内冷却至６００℃以下，与保温时间为２ｈ的无压烧结相比，可降低烧结温度和提高样品密度。力学性能研究结果表明，用放电等离子超快速烧结方法制备的纯氧化铝陶瓷的抗弯强度高达８００ＭＰａ以上，比通常氧化铝陶瓷的抗弯强度高出一倍，用ＳＥＭ研究了在不同温度下超快速烧     

放电等离子超快速烧结氧化物陶瓷

本文介绍一种氧化物陶瓷超快速烧结的新方法．用放电等离子烧结的方法对Al₂O₃、Y-TZP、YAG、Al₂O₃-ZrO₂2和莫来石等各种氧化物粉体进行了超快速烧结,采用2～3min升温到1200℃以上,不保温或保温2min,然后迅即在3min之内冷却至600℃以下的烧结温度,得到了直径为20mm的晶粒细、致密度高、力学性能好的烧结样品．对用化学共沉淀法自制的20mol％Al₂O₃-ZrO₂（3Y）纳米粉体分别在1170～1500℃之间的7个不同温度下进行放电等离子烧结,升温速率为200℃／min,保温2min后;迅即在3min之内强制冷却至600℃以下．1350℃以上烧结得到的样品密度已接近理论密度,1250℃以上烧结得到的样品的断裂韧性K1c都大于6MPa·m^1/2放电等离子超快速反应烧结所得到的ZrO₂-莫来石复相陶瓷致密度高、力学性能好,ZrO₂晶粒在莫来石基体中分布均匀,XRD结果表明,在1530℃烧结的样品中,已找不到ZrsiO₄痕迹,说明在如此快速的烧结条件下;反应烧结已经可以完成．     

快速烧结制备纳米Y-TZP材料

研究了快速热压烧结和放电等离子快速烧结（ＳＰＳ）制备纳米Ｙ－ＴＺＰ材料．利用快速热压烧结和 ＳＰＳ快速烧结,可在烧结温度为 １２００℃、保温９～１０ｍｉｎ条件下,制得相对密度超过９９％的 Ｙ－ＴＺＰ材料．研究发现：虽然快速热压烧结和 ＳＰＳ烧结都可使Ｙ－ＴＺＰ在相同温度下的密度高于普通热压烧结,但两种快速烧结所得Ｙ－ＴＺＰ的晶粒都大于无压烧结所得;另外,快速热压烧结所得样品的结构不够均匀,而ＳＰＳ烧结的样品的均匀性较好．文章对产生这些现象的原因进行了理论探讨．     

Increased leukocyte aggregates are associated with atherosclerosis in patients with hemodialysis

Little data are available on the role of blood rheology in atherosclerosis in hemodialysis (HD) patients. This study sought to assess the relationship between leukocytes conjugated with platelets (leukocyte aggregates [LA]) and atherosclerosis in patients with HD. The present study included 118 patients on HD. As surrogate markers of atherosclerosis, aortic stiffness measured by brachial-ankle pulse wave velocity, and carotid intima-media thickness (IMT) were measured. As an assessment of LA, a method, microchannel array flow analyzer, which makes it possible to directly observe the flow of blood cell elements through the microchannel, was used. We measured a number of LA during 50 μL flow of whole blood through microchannels. In 12 age-matched healthy individuals, a number of LA during 50 μL flow of whole blood was 25.7±5.4, whereas in HD patients it was significantly increased up to 48.2±16.4 (P<0.001). Flow cytometry demonstrated that LA were predominantly monocytes. Leukocyte aggregates were positively associated with plasma levels of fibrinogen (P<0.01), or serum high-sensitive C-reactive protein (P<0.01). Moreover, LA had highly significant associations with brachial-ankle pulse wave velocity (P<0.001) and IMT (P<0.001). In conclusion, we demonstrated hemorheologically that monocyte-platelet conjugates play an important role in aortic stiffness and IMT in HD patients.     

橡胶等静压成型纳米ZrO2(3Y)粉素坯

对橡胶等静压成型(Rubber isostatic pressing,RIP)制备纳米Y-TZP陶瓷作了初步研究.研究结果表明,通过RIP成型,可以获得相对密度较高、体积较大的ZrO₂(3Y)素坯,并在较低温度下无压烧结得到纳米Y-TZP陶瓷.在1100℃下烧结2h所得的Y-TZP陶瓷的相对密度可达97％,晶粒仅为70nm左右.相对密度较高、平均孔径小是RIP成型素坯烧结温度低的主要原因.     

Extraction and Physicochemical Characterization of Pectin from Sunflower Head Residues

Pectin was isolated from sunflower head residues, using 0.75% sodium hexametaphosphate extraction followed by acid precipitation. The yield of pectin was7.3% of the head residues. The isolated pectin contained 89.2% anhydrogalacturonic acid, 2% acetyl ester, and 4.2% neutral sugars, which were mainly rhamnose and glucose. The degree of methylation was 38.5%. The pectin had a high viscosity (527 cp at 1% level) at pH 3 and a high water-holding capacity (57g water/g organic matter). The peak molecular mass of the sunflower pectin was > 523,000 daltons.     

Gelling Characteristics of Pectin From Sunflower Head Residues

Gelling properties of sunflower head pectin were studied using two instrumental methods: the standard sag method and the Instron textural profile method. For the Instron method, the jellies were formulated with 0-60% sugar content with various amounts of calcium chloride (30 to 90 mg/g pectin) at pHs 5.4 and 6.0. Sunflower pectin had a gel power of 110 compared to 100 for a citrus low-methoxyl pectin and 120 for an amidated low-methoxyl pectin. Sunflower pectin formed jellies under all experimental conditions. Sunflower pectin has a high potential for producing low-caloric foods, particularly when a near-neutral taste is required.