A fractional differential constitutive model for dynamic stress intensity factors of an anti-plane crack in viscoelastic materials

Fractional differential constitutive relationships are introduced to depict the history of dynamic stress inten- sity factors （DSIFs） for a semi-infinite crack in infinite viscoelastic material subjected to anti-plane shear impact load. The basic equations which govern the anti-plane deformation behavior are converted to a fractional wave-like equation. By utilizing Laplace and Fourier integral transforms, the fractional wave-like equation is cast into an ordinary differential equation （ODE）. The unknown function in the solution of ODE is obtained by applying Fourier transform directly to the boundary conditions of fractional wave-like equation in Laplace domain instead of solving dual integral equations. Analytical solutions of DSIFs in Laplace domain are derived by Wiener-Hopf technique and the numerical solutions of DSIFs in time domain are obtained by Talbot algorithm. The effects of four parameters α, β, b1, b2 of the fractional dif- ferential constitutive model on DSIFs are discussed. The numerical results show that the present fractional differential constitutive model can well describe the behavior of DSIFs of anti-plane fracture in viscoelastic materials, and the model is also compatible with solutions of DSIFs of anti-plane fracture in elastic materials.

Evaluation of 3-D Printed Immobilisation Shells for Head and Neck IMRT

This paper presents the preclinical evaluation of a novel immobilization system for patients undergoing external beam radiation treatment of head and neck tumors. An immobilization mask is manufactured directly from a 3-D model, built using the CT data routinely acquired for treatment planning so there is no need to take plaster of Paris moulds. Research suggests that many patients find the mould room visit distressing and so rapid prototyping could potentially improve the overall patient experience. Evaluation of a computer model of the immobilization system using an anthropomorphic phantom shows that >99% of vertices are within a tolerance of ±0.2 mm. Hausdorff distance was used to analyze CT slices obtained by rescanning the phantom with a printed mask in position. These results show that for >80% of the slices the median “worse-case” tolerance is approximately 4 mm. These measurements suggest that printed masks can achieve similar levels of immobilization to those of systems currently in clinical use.

Asymmetric Synthesis of (-)-1-Trimethylsilyl-ethanol with Immobilized Saccharomyces Cerevisiae Cells in Water/Organic Solvent Diphasic System

Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.

Continuous Saccharification of Laminarin by Immobilized Laminarinase ULam111 Followed by Ethanol Fermentation with a Marine-Derived Yeast

We isolated a novel laminarinase ULam111 from Flavobacterium sp. strain UMI-01. Purified ULam111 showed degradation activity against laminarin with the specific activity of 224 ± 18 U/mg at 30°C and pH 6.0. Its optimum temperature was 50°C, and degradation activities against laminarin were observed at 4°C - 80°C. With a laminarin degradation system, we investigated the preparation and properties of immobilized ULam111 with the use of the 11 types of carriers. The high activity recoveries of immobilized ULam111 were as follows: 19.4% for IB-S60P carrier beads (the non-ionic type), 15.6% for IB-S60S carrier beads (the non-ionic type), 11.9% for IB-150P carrier beads (the covalent type), and 7.1% for IB-C435 carrier beads (the cationic type). With the repeated use of immobilized ULam111, the enzyme activities immobilized on IB-S60S and those on IB-S60P remained at 40% and 30% respectively after the sixth trial. We selected IB-S60S as suitable beads for enzyme immobilization, and we attempted to construct a reactor system with ULam111 immobilized on IB-S60S beads. In this system, 1.2 - 1.9 g/L glucose was repeatedly produced from 30 mg/mL laminarin solutions after 20 hr when the reactor operation was repeated 10 times. We examined ethanol fermentation from the saccharified solutions with a marine-derived yeast (Saccharomyces cerevisiae C-19), and 0.51 - 0.58 g/L bioethanol was produced from the saccharified solution that contained 1.71 - 1.86 g/L of glucose.

IMMOBILIZATION OF Saccharomyces Cerevisiae USING POLY(ACRYLAMIDE)GEL FOR ASYMMETRIC SYNTHESIS OF R(-)-MANDELIC ACID

In this paper,the poly(acrylamide)hydrogel used to immobilize saccharomyces cerevisiae for asymmetric synthesis of R(-)-mandelic acid was prepared with free radical ploymerization in deionized water at room temperature under nitrogen atmosphere.The influence of the composition of hydrogel,loading amount of cells and culture conditions on the asymmetric synthesis was investigated.Results show that PAAm hydrogel is a feasible carrier for immobilization of cells which is a potential alternative method to prepare enantiomerically pure R(-)-mandelic acid.

Quaternary phosphonium polymer-supported dual-ionically bound[Rh(CO)I_(3)]^(2-)catalyst for heterogeneous ethanol carbonylation

A single-Rh-site catalyst(Rh-TPISP)that was ionically-embedded on a P(V)quaternary phosphonium porous polymer was evaluated for heterogeneous ethanol carbonylation.The[Rh(CO)I_(3)]^(2-)unit was proposed to be the active center of Rh-TPISP for the carbonylation reaction based on detailed Rh L3-edge X-ray absorption near edge structure(XANES),X-ray photoelectron spectroscopy(XPS),and Rh extended X-ray absorption fine structure(EXAFS)analyses.As the highlight of this study,Rh-TPISP displayed distinctly higher activity for heterogeneous ethanol carbonylation than the reported catalytic systems in which[Rh(CO)_(2)I_(2)]^(-)is the traditional active center.A TOF of 350 h^(-1)was obtained for the reaction over[Rh(CO)I_(3)]^(2-),with>95%propionyl selectivity at 3.5 MPa and 468 K.No deactivation was detected during a near 1000 h running test.The more electron-rich Rh center was thought to be crucial for explaining the superior activity and selectivity of Rh-TPISP,and the formation of two ionic bonds between[Rh(CO)I_(3)]^(2-)and the cationic P(V)framework([P]^(+))of the polymer was suggested to play a key role in firmly immobilizing the active species to prevent Rh leaching.

养殖水体氨氮去除的固定化微生物技术

应用固定化技术 ,将富集培养的硝化活性污泥制成固定化小球 ,对固定化小球在不同条件下其硝化活性的影响进行了研究 ;同时 ,采用摇瓶试验比较了固定化小球和悬浮硝化活性污泥对养鳖污水氨氮的处理效果。结果表明 ,固定化小球具有明显抗不利因素的能力 ,降解氨氮的效率稳定 ,对养殖污水氨氮的生物处理具有一定的效果。

适于集约化水产养殖的固定化微生物技术的初步研究

采用生物强化技术尝试建立高效、价廉、实用性强的固定化微生物水质处理技术。根据水产养殖特点,选择了网片、波纹板、竹球等不同载体,对有益微生物制剂进行吸附后,比较其对人工模拟养殖废水处理的效果,最终确定竹球为理想的吸附载体材料;研究了最适母液浓度和吸附时间、水体中作用持续时间等;进行了对不同的商业化微生物制剂与单纯芽孢菌的降解效果比较,得到最佳制剂种类和优化的工艺参数。

磁性固定化纤维素酶的制备及其磁响应性

本研究以磁性壳聚糖微球为载体,采用吸附法制备磁性固定化纤维素酶。以酶活力为考察指标,研究了不同工艺条件对制备固定化酶的影响,及其在外加磁场下的磁响应性的变化。实验结果表明,制备磁性固定化纤维素酶最适条件为:吸附时间10h,pH5.0,离子浓度0.05mol/L,酶用量为150mg。在外加磁场作用下,比较磁性固定化纤维素酶与游离纤维素酶酶活力的变化发现:当磁场强度<500mT与曝磁时间<60min时,游离纤维素酶的酶活随着磁场强度与曝磁时间的增加而增加,但超出此范围,酶活就明显下降;而当磁场强度<300mT与曝磁时间<60min时,磁性固定化纤维素酶酶活与游离纤维素酶的变化趋势相似。

琼脂糖自组装膜基底型免疫芯片载体制备及抗体固定研究

目的:建立具有三维水凝胶结构的琼脂糖自组装膜载体的制备方法,提高免疫芯片对抗体的固定效率。方法:以玻片为载体,采用琼脂糖、高碘酸钠对玻片表面进行修饰,制备琼脂糖自组装膜载体。利用SEM、AFM和FTIR对载体进行表征,获得最佳制备条件。利用荧光显微成像及Image J软件,研究该载体对2种不同种属来源抗体的固定效率,比较琼脂糖自组装膜载体和普通醛基修饰载体对抗体的固定效果。结果:制备的琼脂糖自组装膜载体表面均匀、致密,这种结构比表面积大、抗体固定效率高。制备载体的最佳琼脂糖浓度为1.0%,其固定抗体的最佳浓度为0.3~0.4 mg/ml,琼脂糖自组装膜载体的荧光强度是普通醛基载体的3.94倍。结论:琼脂糖自组装膜是一种理想的固定抗体分子的表面修饰方法,有望用于免疫芯片载体的制备。

固定化与游离态小球藻脱氮除磷对比以及金属镉对吸收磷速率的影响

对固定化与游离态小球藻脱氮、除磷进行对比研究，结果表明固定化藻在两天内对NH4^＋-N和PO4^3- -P的净化效率比悬浮态藻分别高22．49％和35．25％。固定化藻技术不仅保留了悬浮态藻的优点，而且使得藻对氮、磷的去除率有较大的提高。另外，研究了不同光照强度及不同pH值下，小球藻在悬浮和固定状态下镉对污水中正磷酸盐的吸收速率的影响。结果表明，在不同光照强度下，镉总体上降低了小球藻对磷的吸收速率。不同pH值时，无论在悬浮态还是固定态，镉能使小球藻对磷的吸收速率下降20％～30％，由此可见固定处理并没有减少镉的影响。

CT模拟在适形调强放射治疗中的应用研究

目的将CT模拟应用适形调强放射治疗,在临床应用中探索与之相关的一系列更简便和更好的方法,为以后的调强放射治疗提供指南。方法64例肿瘤患者,其中头颈部肿瘤患者42人,胸部肿瘤患者15人,腹部和盆腔肿瘤患者7人。针对不同的患者采取不同的体位固定技术,做CT\MRI扫描,采用两种标记法标记坐标系并比较了两种方法特点,然后做三维重建、图像融合、射野布置,并对靶中心做了验证。结果CT模拟可以大大提高治疗位置的精确度,更好地避开和保护重要器官,使其受到较低的剂量,而靶区受到高适形剂量。内标记方法的位置精读和CT扫描的层厚无关,而外标记法的位置精读与扫描层厚相关。头颈部肿瘤靶点偏差小于3mm,胸部肿瘤、腹部和盆腔肿瘤,靶点偏差均小于5mm。结论CT模拟定位是适形调强放射治疗必不可少的工具,但还需更好的解决体位的固定和器官运动等问题;内外标记同时采用的方法,是一种安全、准确的方法,图像融合智能化还需要加强;三维适形的布野原则对调强放疗的布野有指导意义;采用X光模拟机验证靶中心也是一种方便可靠的方法。

胶红酵母固定化方法研究

研究胶红酵母固定化方法,并测定所得固定化细胞的机械强度和通透性,对固定化方法进行初步筛选;研究磷酸缓冲溶液对固定化细胞强度的影响,最终得到目的固定化方法。试验表明:CA-活性炭(C)复合凝胶包埋所得固定化细胞,经0.6%聚乙烯亚胺(PEI)强化12 h,再经1%的戊二醛强化3 h后,机械强度大大提高,能耐磷酸缓冲液。

一组十二烷基苯磺酸钠生物降解的新研初探

将超声波和固定化细胞技术相结合,以阴离子表面活性剂废水中直链十二烷基苯磺酸钠(LAS)为研究对象,研究了低强度超声波作用于固定化微生物细胞对LAS降解的主要影响因素,并通过正交实验,以LAS的降解率r为主要指标,研究了低强度超声波干预的参数条件,结果表明:一定频率参数的低强度超声波能有效增强固定化细胞的生物活性并促进固定化细胞传质,实验以LAS初始浓度c为50mg/L的模拟废水为对象,在最适超声条件下LAS的降解率最高达83%,比固定化细胞不加载超声组提高9.5%以上。

鼻咽癌调强放疗两种体位固定方式的摆位误差分析

目的分析鼻咽癌调强放疗两种不同体位固定方式的摆位误差。方法选取我院收治的72例鼻咽癌患者,按患者不同的固定方式分为常规联合固定组和发泡胶联合固定组各36例。两组均采用调强放射治疗,常规联合固定组采取标准化树脂头枕联合头颈肩热塑面罩进行体位固定,发泡胶联合固定组采取发泡胶联合头颈肩热塑面罩进行体位固定。比较两组患者的头部放疗靶区摆位和放疗颈椎区域摆位的线性误差及旋转误差。结果发泡胶联合固定组的头部放疗靶区摆位左右、前后、上下线性误差均小于常规联合固定组(P<0.05);两组的头部放疗靶区摆位左右、前后、上下旋转误差比较均无统计学差异(P>0.05)。发泡胶联合固定组的放疗颈椎区域摆位左右、前后、上下线性误差均小于常规联合固定组(P<0.05);发泡胶联合固定组的放疗颈椎区域摆位左右、前后、上下旋转误差均小于常规联合固定组(P<0.05)。结论鼻咽癌调强放射治疗中,采取发泡胶进行体位固定效果较好,可减小头部放疗靶区摆位、放疗颈椎区域摆位线性误差及放疗颈椎区域旋转误差,有效提高调强放疗精度,对改善临床疗效具有重要意义。

热塑膜固定底板对IMRT计划三维剂量验证通过率的影响与修正

目的:分析和评估一款热塑膜固定底板对调强放射治疗(IMRT)计划三维剂量验证通过率的影响,并对其进行剂量修正。方法:利用Octavius 4D三维剂量验证系统,对60例IMRT计划按照后入射野数占总射野数比值分成6组,分别进行仅有床板和有床板与热塑膜固定底板组合的三维剂量验证,以评估热塑膜固定底板对IMRT三维剂量验证通过率的影响。然后对入射野数占比最大的第6组进行剂量修正,并与修正前的γ通过率进行比较,评估剂量修正的作用。结果:未考虑固定底板时,6组IMRT计划γ通过率分别为:98.00%、96.87%、96.76%、94.82%、95.51%、95.32%;考虑固定底板以后分别为:98.88%、96.46%、95.85%、93.12%、93.22%、89.07%,考虑前后P值分别为0.147、0.534、0.406、0.051、0.030(t=2.566)、0.000(t=5.637),第5组和第6组有统计学差异。对第6组进行固定底板剂量修正以后,γ通过率平均为94.90%,提高5.8%。结论:热塑膜固定底板对IMRT计划三维剂量验证通过率有一定的影响,且当IMRT计划的后入射野数所占总射野数比值越大,影响越大,临床制定计划时有必要对固定底板进行剂量修正。

体位固定装置对鼻咽癌调强计划的剂量学影响

目的:研究头颈体位固定装置对鼻咽癌调强放射治疗计划的剂量影响。方法:随机选取9例鼻咽癌患者,对每例患者勾画两套外轮廓集合,一套仅勾画患者正常外轮廓(Plan_(without)),另一套勾画包含固定装置的外轮廓(Plan_(with))。对每例患者的两套轮廓分别设计9野调强和单弧VMAT计划。通过比较计划间的DVH参数结果、两个计划结果相减来评估头颈固定装置引起的剂量学差异。结果:对9野调强计划,Plan_(with)的靶区覆盖和平均剂量(D_(mean))相对Plan_(without)计划均有所减小。鼻咽部肿瘤靶区(GTVnx)、颈部淋巴结肿瘤靶区(GTVnd)、临床靶区与高危淋巴引流区(CTV1)以及预防照射淋巴引流区(CTV2)外扩3 mm得到的PTVnx、PTVnd、PTV1和PTV2处方剂量覆盖分别降低2.14%、10.34%、0.88%、2.86%(P<0.01、P<0.01、P=0.15、P<0.01),D_(mean)减小0.96%、1.94%、1.07%、1.26%(P值均<0.01);除脑干外各危及器官D_(mean)均有减小(最大偏差1.69%),且P值均≤0.01;后颈的皮肤剂量增加约10～15 Gy。对于VMAT,Plan_(with)的靶区覆盖和D_(mean)均减小:PTVnx、PTVnd、PTV1和PTV2处方剂量覆盖分别降低2.56%、22.42%、0.66%、1.30%(P<0.01、P=0.57、P<0.01、P=0.02),平均剂量分别减小了0.86%、2.45%、0.93%、1.59%(P=0.01、P<0.01、P<0.01、P<0.01);各危及器官的D_(mean)均有减小(最大1.60%),且P值均<0.01;同时,体位固定装置的存在使得入射固定装置的射线的散射和体表建成发生变化,后颈的皮肤剂量增加约6～14 Gy。结论:头颈固定装置会引起射线的衰减和建成效应变化,使得鼻咽癌计划靶区的覆盖和D_(mean)均有降低,在计划设计时需要将其包括到外轮廓内,以保证剂量计算的准确性。

碳纤维固定底板对放射治疗射野剂量分布影响的初步研究

目的:分析碳纤维固定底板对放射治疗中射线的衰减作用及引起的调强射野MatriXX剂量验证结果的变化,研究该固定底板对放射治疗射野剂量分布的影响。方法:选取20例宫颈癌患者,固定野调强计划中机架角度为180°的射野,制作相应的验证计划,在Varian Clinac iX加速器上执行验证计划,使用二维电离室矩阵MatriXX进行测量。使用ORFIT AIO碳纤维固定底板,对加速器机头与MatriXX之间无底板(A组)、有1块底板(B组)、2块底板(C组)和3块底板(D组)的4组情形进行研究。使用OmniPro I'm RT软件获得4组情形的数据,对射野平面内最大剂量点及射野的γ射线通过率进行统计分析。结果:B组、C组和D组的情形与A组相比较,其射野平面内最大剂量点对射线的平均衰减因子分别为:B组(1.73±0.11)%、C组(3.44±0.36)%和D组(5.48±0.44)%。4组情形射野γ射线通过率的平均值分别为:A组(94.87±2.31)%、B组(99.18±0.61)%、C组(99.79±0.27)%和D组(96.24±1.99)%,B组、C组和D组与A组比较,组间差异有统计学意义(t=9.788,t=9.261,t=2.256;P<0.05)。结论:碳纤维固定底板对高能X射线有一定的衰减作用,对通过底板的射野的剂量分布有一定影响,物理师在设计计划进行剂量计算时,应考虑碳纤维固定底板对射野剂量分布的影响。

杏鲍菇液体菌种的细胞固定化技术及其保藏条件研究

为解决杏鲍菇液体菌种不耐储存和不易运输等问题,通过筛选适宜的固定化载体种类及其质量浓度,分析液体菌种与固定化载体体积比、CaCl_(2)质量浓度、交联时间等对固定化小球形成的影响,优化固定化条件,研究杏鲍菇液体菌种细胞固定化技术;通过测定不同温度条件下保藏不同时间固定化菌种的成活率、菌丝生长速度、呼吸强度、纤维素酶活性等,明确固定化菌种的生物活性和保藏稳定性。结果表明,杏鲍菇液体菌种的细胞固定化最佳条件为:将海藻酸钠与聚乙烯醇(质量比3∶7)作为固定化载体,固定化载体质量浓度为80 g/L,液体菌种与固定化载体溶液体积比5∶5,CaCl_(2)质量浓度为20 g/L,交联时间6 h,制得的固定化菌种球形规则,传质性快,为15 min,机械强度适中,为60.1 g,菌丝增长率高达200.1%。固定化菌种在20、4℃条件下保藏30 d,随着保藏时间增加,成活率和菌丝生长速度无显著性变化,呼吸强度降低,纤维素酶活性升高,说明菌种仍具有较高的生物活性,利于固定化菌种生物活性稳定;-20℃保藏10 d成活率和菌丝生长速度分别降低50个百分点和72.73%,呼吸强度和纤维素酶活性显著降低,菌种生物活性降低,不利于菌种的保藏。

颈胸段食管癌调强放疗中两种固定方式对摆位误差的影响

目的对比热塑头颈肩膜及体膜固定在颈胸段食管癌调强放疗中的摆位误差,探讨更合适的体位固定方式。方法对16例颈段及胸上段食管癌调强放疗的患者随机采用热塑头颈肩膜(头颈肩膜组)和体膜(体膜组)固定,每组8例,在首次放疗前及放疗中进行锥形束CT(CBCT)扫描,对比分析两组左右、上下、前后方向上的摆位误差。并将CBCT图像分别以环甲膜、锁骨头及气管隆突为中心区域与相应的计划图像进行分段配准,对比分析两组不同区域的摆位误差。结果 16例患者共获得60次CBCT图像,其中头颈肩膜组28次,体膜组32次。头颈肩膜组在上下方向相对误差大于体膜组(P=0.004);在左右方向头颈肩膜组的绝对误差大于体膜组(P=0.036)、在上下方向的体膜组绝对误差大于头颈肩膜组(P=0.001)。在环甲膜区,体膜组上下、前后方向的绝对误差均大于头颈肩膜组(P=0.020/0.024)。在隆突区头颈肩膜组左右方向绝对误差大于体膜组(P=0.012)。结论两种固定方式在不同方向上的摆位误差各有优劣,但均在可控范围内,在临床中建议对于病变中心偏向胸部的患者选择体膜固定,对于病变中心偏向颈部或锁骨区的患者选择头颈肩膜固定效果更好。