A novel endorectal RF coil for high resolution MRI and spectroscopy of the prostate

MRI is a non invasive powerful imaging tool andhas been used in the diagnosis of various prostate dis eases. The excellent soft tissue contrast provided byMRI allows improved visualization of the prostateanatomy, surrounding critical structures (such as theneurovascular bundles and periurethral zone), and theextent of tumor spread. This improved contrast reso lution presents a distinct advantage over otherprostate imaging modalities such as transrectal ultra sound and comp…     

A novel endorectal RF coil for high resolution MRI and spectroscopy of the prostate

The diagnosis of prostate diseases by magnetic resonance imaging (MRI) in vivo is sometimes difficult for the lower signal to noise ratio (SNR). To increase the SNR of the prostate image, we designed a RF coil that can be inserted into rectum and was named endorectal coil. The properties of RF coil were evaluated using a network analyzer. Moreover the images and spectroscopy of a special phantom were acquired and the results were compared to those of the commercial TORSO coil (G.E. Medical Systems, USA). Our coil gave a significantly higher SNR at the region of interest (ROI). The achieved high local SNR and resulting high spatial resolution would add more anatomic and biochemical information to the diagnosis of prostate diseases.     

Extinction and Stationary Distribution of a Stochastic SIR Epidemic Model with Jumps

A stochastic susceptible-infective-recovered(SIR)epidemic model with jumps was considered.The contributions of this paper are as follows.(1) The stochastic differential equation(SDE)associated with the model has a unique global positive solution;(2) the results reveal that the solution of this epidemic model will be stochastically ultimately bounded,and the non-linear SDE admits a unique stationary distribution under certain parametric conditions;(3) the coefficients play an important role in the extinction of the diseases.     

相位对比磁共振成像中的扰相射频脉冲分析

应用仿真实验研究了在基于梯度回波的2维相位对比磁共振序列中扰相射频脉冲的作用,应用模体和志愿者实验来确定在准确测量血流的前提下扰相射频脉冲对相位对比磁共振图像和血流测量结果的影响.相位对比磁共振对血流的测量结果显示:当扰相梯度充足时,是否使用扰相射频脉冲对测量结果无明显影响;但是当扰相梯度不充分时,使用扰相射频脉冲成像测量的血流更准确;并且使用扰相射频脉冲可以改善图像的对比度,更容易区分血流区域和静态组织.     

Stochastic differential equation software reliability growth model with change-point

This paper presents software reliability growth models （SRGMs） with change-point based on the stochastic differential equation （SDE）.Although SRGMs based on SDE have been developed in a large scale software system,considering the variation of failure distribution in the existing models during testing time is limited.These SDE SRGMs assume that failures have the same distribution.However,in practice,the fault detection rate can be affected by some factors and may be changed at certain point as time proceeds.With respect to this issue,in this paper,SDE SRGMs with changepoint are proposed to precisely reflect the variations of the failure distribution.A real data set is used to evaluate the new models.The experimental results show that the proposed models have a fairly accurate prediction capability.     

Cs-131近距离治疗前列腺癌剂量学的蒙特卡罗模拟

利用MCNP程序对IsoRay公司2004年研制的并通过FDA认证的Cesium-131即model Cs-1放射源近距离治疗前列腺癌的各剂量学参数进行研究．采用美国可视人项目（VHP）确定的成年男子全身模型的前列腺参数替代传统的用组织等效水体模．所得到的径向剂量函数、各向异性函数等可直接应用于临床治疗的剂量计算．     

半解析方法中圆形等效源法的前处理算法

应用计算机图形学的原理和方法,提出了一种求解数学上极值问题的扫描-生长算法,解决了二维场的圆形分割问题.该算法能够快速确定分割区域中多个极点(各分割圆的圆心)的位置和数量,达到了用尽量少的圆形数来最大限度地充满该分割区域,并能满足在需要处(如场量突变处)进行局部加密的要求.根据为广义多极技术(属半解析法范畴)创建的理论体系,这些极点确定了解函数在级数展开式中各变量的起点.正因为这些变量的准确定位,不仅克服了广义多极技术中极点位置设置的盲目性,而且提高了解的计算效率和计算精度.因此,扫描-生长算法还可推广应用于轴对称场的计算中.     

一种多极阵列声波测井重要特征分析方法

文章讨论了多极阵列声波测井的原理和面临的问题,利用粗集理论的方法,分析了影响多极阵列声波测井结果的系统特征的重要性,并结合某一油田测井数据进行了应用。     

Comparison of volatile and semivolatile compounds from commercial cigarette by supercritical fluid extraction and simultaneous distillation extraction

Supercritical carbon dioxide fluid extraction (SFE) was studied as a rapid method for extraction of volatile and semivolatile compounds of Chinese commercial cigarettes. The method was compared with simultaneous distillation and extraction (SDE). Temperature and pressure for the SFE were optimized. The extracts obtained by the two methods showed different characters in composition and represented differently the flavor characteristics of tobacco; compared to SDE, SFE can extract compounds within a shorter time and avoid the thermal degradation and solvent contamination of samples. The extracts by the two extraction methods are complementary for investigating the flavor characteristic of tobacco products.     

血啉甲醚-光动力学疗法去除大鼠前列腺增生的实验研究

以丙酸睾酮诱导的大鼠前列腺增生为研究对象,观察光动力学疗法(PDT)对大鼠前列腺增生的治疗作用.研究结果表明:单纯激光照射或单纯注射光敏剂对大鼠前列腺增生无显著影响(P>0.05);大鼠经各PDT治疗组治疗后,前列腺体积均明显减小,前列腺指数明显下降,与动物模型组存在明显差异(P均小于0.01),说明光动力疗法对前列腺增生细胞具有杀伤和抑制生长作用.     

遗传算法优化性能评价准则研究

为了克服传统遗传算法优化性能评价准则（如在线性能、离线性能）忽略随机因素对算法的影响，从而不能准确评价算法性能的缺点，提出了一种基于平均偏离距和偏离距标准差的新的遗传算法优化性能评价准则，给出了平均偏离距和偏离距标准差的数学定义，并分析了它们的泛函意义．由于平均偏离距和偏离距标准差采用遗传算法多次运行结果的统计参数来评价算法的性能，因此能够较好地消除随机因素对算法性能的影响．同时，应用所提出的评价准则研究了二进制码和格雷码对遗传算法优化性能的影响．基于F2函数的数值实验结果表明，与二进制码相比，格雷码的平均偏离距和偏离距标准差指标都比较低，因此能够更好地提高遗传算法的优化性能．     

快速多极边界元方法在二维声散射问题中的应用

快速多极算法(FMM)是求解边界元方法(BEM)在大尺度情况下的一种非常有效的算法.研究了快速多极算法在二维声散射问题的边界积分方程求解中的应用.给出了积分核函数以及其共轭积分算子核函数的多极展开式,局部展开式以及相应展开系数之间的转化关系.分别应用两种不同的层级树结构的FMM来进行求解,并对两种树结构下的求解效率进行了对比.数值算例表明用快速多极算法求解该问题时在存储量和计算量上比直接求解方法效率更高.     

Generation of a prostate from a single adult stem cell

The existence of prostate stem cells (PSCs) was first postulated from the observation that normal prostate regeneration can occur after repeated cycles of androgen deprivation and replacement in rodents. Given the critical role of PSCs in maintaining prostate tissue integrity and their potential involvement in prostate tumorigenesis, it is important to define specific markers for normal PSCs. Several cell-surface markers have been reported to identify candidate PSCs, including stem cell antigen-1 (Sca-1, also known as Ly6a), CD133 (Prom1) and CD44 (refs 3-10). However, many non-PSCs in the mouse prostate also express these markers and thus identification of a more defined PSC population remains elusive. Here we identify CD117 (c-kit, stem cell factor receptor) as a new marker of a rare adult mouse PSC population, and demonstrate that a single stem cell defined by the phenotype Lin(-)Sca-1(+)CD133(+)CD44(+)CD117(+) can generate a prostate after transplantation in vivo. CD117 expression is predominantly localized to the region of the mouse prostate proximal to the urethra and is upregulated after castration-induced prostate involution-two characteristics consistent with that of a PSC marker. CD117(+) PSCs can generate functional, secretion-producing prostates when transplanted in vivo. Moreover, CD117(+) PSCs have long-term self-renewal capacity, as evidenced by serial isolation and transplantation in vivo. Our data establish that single cells in the adult mouse prostate with multipotent, self-renewal capacity are defined by a Lin(-)Sca-1(+)CD133(+)CD44(+)CD117(+) phenotype.     

固相微萃取与同时蒸馏萃取-气质联用法提取牛角瓜中挥发性物质比较

采用固相微萃取法(SPME)和同时蒸馏萃取法(SDE)提取牛角瓜中挥发性成分,联合气质联用技术进行分析.结果表明,利用两种提取方法从牛角瓜中共鉴别出163个化合物,其中固相微萃取法鉴定了81个化合物,而同时蒸馏萃取法鉴定了82个化合物,共有的化合物为30个.     

电场计算的快速多极子预条件高阶边界元法

针对多介质工频电场计算中低阶边界元法及预条件(GMRES)法的计算精度低及计算成本高的不足,在低阶边界元法基础上引入高阶边界元和快速多极子法,提出了一种用于求解三维电场分布的快速多极子预条件GMRES高阶边界元法。建立了三维电场计算高阶边界元模型,阐述了快速多极子预条件GMRES高阶边界元法基本原理和具体实现方法;通过双介质实验模型进行了方法验证,并基于500kV变电站部分关键设备的三维电场计算,表明该方法在电场计算精度及在内存消耗和计算时间上均比预条件GMRES法有明显的优势。最后将计算结果与实际测量值进行了比较,该方法的计算结果与测量值最大相对误差为8.65%,该方法更适合于分析变电站这种大尺度多介质环境下的工频电场分布。     

随机森林赋权层次分析法的崩塌易发性评价

为确定一组合适的指标权重,通过提出随机森林(random forest, RF)模型与层次分析法(analytic hierarchy process, AHP)相结合的模型对不同指标进行客观赋权重,以区分不同指标对崩塌易发性的影响。该耦合模型利用RF模型计算出各指标的客观权重,作为层次分析法的初始权重来修正判断矩阵,最终获得各指标的综合权重。以陕西省绥德县为研究对象,通过分析大量文献及进行相关性分析后选取坡向、曲率、坡度、地貌、降雨量、距水系距离、地层岩性、距道路距离及归一化植被指数(normalized vegetation index, NDVI)9个影响因子作为评价指标,结合ArcGIS空间分析功能,采用RF模型、RF-AHP模型进行崩塌易发性评价,评价结果用受试者特征曲线(receiver operate curve, ROC)进行检验。结果表明:影响崩塌的9个评价指标中,距水系距离对其影响最大;崩塌高易发区呈线性分布在水系及道路附近;RF-AHP模型较RF模型的预测精度提高了4.5%。说明RF-AHP模型更适合此研究区的崩塌易发性评价,评价结果可为绥德县防灾减灾工作提供理论指导。     

香椿挥发性成分的分析

采用同时蒸馏萃取和水蒸汽蒸馏的方法分别对山东寿光产的香椿芽及茎的挥发性成分进行了提取,并且利用GC／MS方法对提取的挥发性成分进行了鉴定．从同时蒸馏萃取和水蒸汽蒸馏提取的香持芽挥发油中分别鉴定了42种和36种化学成分;从香椿茎中各鉴定了30种化学成分,并且比较了两种方法及两个部位挥发性成分的不同。     

Experimental studies on the effects of porosity on acoustic resonance spectroscopy for synthetic porous rock samples in a cylindrical resonant cavity

Based on our previous work on acoustic resonance spectroscopy （ARS） measurement, the ARSs in low frequency modes were measured for 10 synthetic oil-saturated rock samples with the porosities ranging from 22% to 30%, and the effects of porosity on ARS of the synthetic porous rock samples in a cylindrical resonant cavity were studied. The experimental results show that as the location of a synthetic rock sample changes from the top to the middle of the resonant cavity, the resonance frequency （RF） will gradually increase and the corresponding resonance amplitude （RA） will decrease. In the middle of the cavity, the RF reaches its maximum, while the RA reaches its minimum. When the synthetic rock porosity increases, the RF will decrease and the RA will decrease. Furthermore, the RF of a synthetic rock sample was numerically calculated with an average volume model in the resonant cavity. Our numerical results show that as the location of the sample changes from the top to the middle of the cavity, the RF gradually increases and the RF reaches its maximum value in the middle of the cavity. However, the RF decreases as the porosity of the sample increases in the middle of the cavity. The porosity effects on the ARS described above were confirmed by our experimental result as well as the theoretical analyses, which is important for porosity and fracture characterizations in a rock sample using the ARS in a low frequency mode.     

不同提取方法对琯溪蜜柚果皮精油性质及组分的影响

］以琯溪蜜柚果皮为原料,研究了蒸馏法和同时蒸馏萃取法对蜜柚精油性质及组分的影响.结果显示:两种方法提取所得蜜柚精油为黄色澄清液体,具有新鲜蜜柚果皮的特征香气,所得精油理化指标相差不大,均具有良好的品质.利用气质联用技术对精油进行组分鉴定分析得知:蜜柚果皮精油中的主要成分为d-柠檬烯、β-月桂烯、圆柚酮、吉马烯、香叶醇,新鲜果皮精油中柠檬烯含量最高,占总量的52.37%;其次为β-月桂烯,占26.07%.同时蒸馏萃取法所得精油中圆柚酮的质量分数（8.64%）是蒸馏法的（3.43%）两倍多