目的优化点分辨波谱(PRESS)的回波时间(TE),以检测胶质瘤中的胱硫醚,并评估PRESS波谱在识别1p/19q共缺失分子分型方面的诊断准确性。方法通过计算机模拟激发和模体实验优化PRESS的TE,以更好地区分胱硫醚和重叠的天冬氨酸多重峰。随后,...目的优化点分辨波谱(PRESS)的回波时间(TE),以检测胶质瘤中的胱硫醚,并评估PRESS波谱在识别1p/19q共缺失分子分型方面的诊断准确性。方法通过计算机模拟激发和模体实验优化PRESS的TE,以更好地区分胱硫醚和重叠的天冬氨酸多重峰。随后,将优化后的PRESS序列和97 ms TE PRESS序列应用于前瞻性纳入的84例疑似胶质瘤或胶质瘤复发的患者。通过拟合包含和不包含天冬氨酸的基组集来研究天冬氨酸对胱硫醚量化的影响,并评估PRESS对1p/19q共缺失胶质瘤的诊断表现。结果PRESS的TE优化为TE=45 ms,胱硫醚和天冬氨酸的谱峰模式在模拟激发和模体实验中一致。在临床实验中,97 ms TE PRESS中不包含天冬氨酸拟合得到的胱硫醚平均浓度显著高于使用完整基组集拟合的浓度[(1.97±2.01)mM vs.(1.55±1.95)mM,P<0.01],而45 ms TE PRESS方法则无显著差异[(0.801±1.217)mM vs.(0.796±1.217)mM,P=0.494]。45 ms方法的胱硫醚浓度与编辑MRS的相关性优于97 ms方法(r=0.68 vs.0.49,P<0.01)。在鉴别1p/19q共缺失胶质瘤方面,45 ms TE PRESS的敏感度和特异度分别为66.7%和73.7%,97 ms TE PRESS的敏感度和特异度分别为44.4%和52.5%。结论45 ms TE PRESS较97 ms方法提供了更精确的胱硫醚检测,将有助于1p/19q共缺失胶质瘤的无创诊断和患者的治疗反应监测。PRESS在1p/19q共缺失胶质瘤中表现出中等诊断性能,表明需要进一步研究。展开更多
We have witnessed the tremendous momentum of the second spring of parallel computing in recent years. But, we should remember the low points of the field more than 20 years ago and review the lesson that has led to th...We have witnessed the tremendous momentum of the second spring of parallel computing in recent years. But, we should remember the low points of the field more than 20 years ago and review the lesson that has led to the question at that point whether ＂parallel computing will soon be relegated to the trash heap reserved for promising technologies that never quite make it＂ in an article entitled ＂the death of parallel computing＂ written by the late Ken Kennedy -- a prominent leader of parallel computing in the world. Facing the new era of parallel computing, we should learn from the robust history of sequential computation in the past 60 years. We should study the foundation established by the model of Tuhring machine （1936） and its profound impact in this history. To this end, this paper examines the disappointing state of the work in parallel Turing machine models in the past 50 years of parallel computing research. Lacking a solid yet intuitive parallel Turing machine model will continue to be a serious challenge in the future parallel computing. Our paper presents an attempt to address this challenge by presenting a proposal of a parallel Turing machine model. We also discuss why we start our work in this paper from a parallel Turing machine model instead of other choices.展开更多
The construction of large software systems is always achieved through assembly of independently written components -- program modules. For these software components to work together, they must share a common set of da...The construction of large software systems is always achieved through assembly of independently written components -- program modules. For these software components to work together, they must share a common set of data types and principles for representing structured data such as arrays of values and files. This common set of tools for creating and operating on data objects is provided by the infrastructure of the computer system： the hardware, operating system and runtime code. Because the nature and properties of these tools are crucial for correct operation of software components and their inter-operation, it is essential to have a precise specification that may be used for verifying correctness of application software on one hand, and to verify correctness of system behavior on the other. We call such a specification a program execution model （PXM）. It is evident that the properties of the PXM implemented by a computer system can have serious impact on the ability of application programmers to practice modular software construction. This paper discusses the concept of program execution models and presents a set of principles that a PXM must satisfy to provide a sound basis for modular software construction. Because parallel program execution on computer systems with many processing units is an essential part of contemporary computing environments, the expression of parallelism and modular software construction using components involving parallel operations is included in this treatment. The conclusion is that it is possible to build computer systems that implement a PXM within which any parallel program may be used, unmodified, as a component for building more substantial parallel programs.展开更多
文摘目的优化点分辨波谱(PRESS)的回波时间(TE),以检测胶质瘤中的胱硫醚,并评估PRESS波谱在识别1p/19q共缺失分子分型方面的诊断准确性。方法通过计算机模拟激发和模体实验优化PRESS的TE,以更好地区分胱硫醚和重叠的天冬氨酸多重峰。随后,将优化后的PRESS序列和97 ms TE PRESS序列应用于前瞻性纳入的84例疑似胶质瘤或胶质瘤复发的患者。通过拟合包含和不包含天冬氨酸的基组集来研究天冬氨酸对胱硫醚量化的影响,并评估PRESS对1p/19q共缺失胶质瘤的诊断表现。结果PRESS的TE优化为TE=45 ms,胱硫醚和天冬氨酸的谱峰模式在模拟激发和模体实验中一致。在临床实验中,97 ms TE PRESS中不包含天冬氨酸拟合得到的胱硫醚平均浓度显著高于使用完整基组集拟合的浓度[(1.97±2.01)mM vs.(1.55±1.95)mM,P<0.01],而45 ms TE PRESS方法则无显著差异[(0.801±1.217)mM vs.(0.796±1.217)mM,P=0.494]。45 ms方法的胱硫醚浓度与编辑MRS的相关性优于97 ms方法(r=0.68 vs.0.49,P<0.01)。在鉴别1p/19q共缺失胶质瘤方面,45 ms TE PRESS的敏感度和特异度分别为66.7%和73.7%,97 ms TE PRESS的敏感度和特异度分别为44.4%和52.5%。结论45 ms TE PRESS较97 ms方法提供了更精确的胱硫醚检测,将有助于1p/19q共缺失胶质瘤的无创诊断和患者的治疗反应监测。PRESS在1p/19q共缺失胶质瘤中表现出中等诊断性能,表明需要进一步研究。
文摘We have witnessed the tremendous momentum of the second spring of parallel computing in recent years. But, we should remember the low points of the field more than 20 years ago and review the lesson that has led to the question at that point whether ＂parallel computing will soon be relegated to the trash heap reserved for promising technologies that never quite make it＂ in an article entitled ＂the death of parallel computing＂ written by the late Ken Kennedy -- a prominent leader of parallel computing in the world. Facing the new era of parallel computing, we should learn from the robust history of sequential computation in the past 60 years. We should study the foundation established by the model of Tuhring machine （1936） and its profound impact in this history. To this end, this paper examines the disappointing state of the work in parallel Turing machine models in the past 50 years of parallel computing research. Lacking a solid yet intuitive parallel Turing machine model will continue to be a serious challenge in the future parallel computing. Our paper presents an attempt to address this challenge by presenting a proposal of a parallel Turing machine model. We also discuss why we start our work in this paper from a parallel Turing machine model instead of other choices.
文摘The construction of large software systems is always achieved through assembly of independently written components -- program modules. For these software components to work together, they must share a common set of data types and principles for representing structured data such as arrays of values and files. This common set of tools for creating and operating on data objects is provided by the infrastructure of the computer system： the hardware, operating system and runtime code. Because the nature and properties of these tools are crucial for correct operation of software components and their inter-operation, it is essential to have a precise specification that may be used for verifying correctness of application software on one hand, and to verify correctness of system behavior on the other. We call such a specification a program execution model （PXM）. It is evident that the properties of the PXM implemented by a computer system can have serious impact on the ability of application programmers to practice modular software construction. This paper discusses the concept of program execution models and presents a set of principles that a PXM must satisfy to provide a sound basis for modular software construction. Because parallel program execution on computer systems with many processing units is an essential part of contemporary computing environments, the expression of parallelism and modular software construction using components involving parallel operations is included in this treatment. The conclusion is that it is possible to build computer systems that implement a PXM within which any parallel program may be used, unmodified, as a component for building more substantial parallel programs.
