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相关概念视频

Test for Homogeneity01:23

Test for Homogeneity

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The goodness–of–fit test can be used to decide whether a population fits a given distribution, but it will not suffice to decide whether two populations follow the same unknown distribution. A different test, called the test for homogeneity, can be used to conclude whether two populations have the same distribution. To calculate the test statistic for a test for homogeneity, follow the same procedure as with the test of independence. The hypotheses for the test for homogeneity can...
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Glassware Calibration01:11

Glassware Calibration

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Accurate calibration of glassware, such as volumetric flasks, pipettes, and burettes, is essential to ensure accurate measurements in the analytical laboratory. Calibration helps maintain consistency across measurements and prevents errors arising from inaccurate volumes.
Volumetric flasks: Volumetric flasks are designed to prepare aqueous solutions of precise volumes accurately with a calibration line on the neck. To calibrate a volumetric flask, it is important to fill it with distilled...
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Pulse01:16

Pulse

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When the heart pumps blood out, arterial elastic fibers play a crucial role in sustaining a high-pressure gradient. They expand to accommodate the received blood and then recoil - a process known as the pulse that can be either manually palpated or electronically quantified. Despite a reduction in its effect with increased distance from the heart, elements of the pulse's systolic and diastolic components persist, observable even at the arteriole level.
The pulse serves as a clinical...
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Pulse01:05

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The pulse is one of the most fundamental physiological indicators of the body's cardiovascular health. It is the rhythmic expansion and contraction of the arterial walls in response to the pressure generated by the heart's pumping action.
Pulse Rate and its Significance
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Instrument Calibration01:12

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Instrument calibration is essential for ensuring that instruments produce accurate and consistent results. It is vital in manufacturing, healthcare, testing laboratories, and scientific research. Calibration processes are specific to each instrument and help enhance data accuracy. Each instrument has a unique calibration process tailored to its design and function to improve data accuracy.
Analytical Balance Calibration
An analytical balance measures mass and requires regular calibration to...
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Plotting and Calibrating the Root Locus01:19

Plotting and Calibrating the Root Locus

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Root loci often diverge as system poles shift from the real axis to the complex plane. Key points in this transition are the breakaway and break-in points, indicating where the root locus leaves and reenters the real axis. The branches of the root locus form an angle of 180/n degrees with the real axis, where n is the number of branches at a breakaway or break-in point.
The maximum gain occurs at the breakaway points between open-loop poles on the real axis, while the minimum gain is...
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Spatial Separation of Molecular Conformers and Clusters
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无校准的GRAPE pTx脉冲用于7T时均的空间选择性激发.

Daniel Löwen1, Eberhard D Pracht1, Marten Veldmann1

  • 1MR Physics, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.

Magnetic resonance in medicine
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概括

新的通用GRAPE脉冲为MRI提供了改进的空间选择. 这些光谱选择性脉冲增强了信号噪声比和强度,推进了7TMRI技术.

关键词:
抓 (GRAPE) 是一种抓方式.平行传输的平行传输方式超高波场的超高波场是什么?全球脉冲是一种普遍的脉冲.

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科学领域:

  • 磁共振成像 (MRI) 是一种磁共振成像技术.
  • 无线电频率 (RF) 脉冲设计
  • 高场磁共振成像 (MRI) 是一种高场磁共振成像.

背景情况:

  • 渐变重定焦回声获取 (GRASE) 脉冲对于MRI至关重要.
  • 为光谱选择性和空间定位优化射频脉冲是一个持续的挑战.
  • 现有的方法可能在同质性,信号噪声比 (SNR) 和稳定性方面存在局限性.

研究的目的:

  • 扩展通用脉冲GRAPE (梯度重定焦回声获取) 形式主义,以纳入定义的光谱响应.
  • 应用这种扩展形式主义来实现MRI中的空间选择.
  • 为了评估这些光谱选择性,空间选择性GRAPE脉冲的性能.

主要方法:

  • 通过结合多个频率的布洛赫模拟,开发了通用光谱选择性GRAPE脉冲.
  • 通过在脉冲计算过程中叠加一个恒定的梯度场来实现空间选择.
  • 在切片和板块选择性成像实验中测试了开发的脉冲.

主要成果:

  • 全球空间选择性GRAPE脉冲显示出改善的翻转角度 (FA) 同质性和SNR.
  • 与传统的射频脉冲相比,在2D梯度回声中实现了大约6%的SNR增加.
  • 与k-T-spoke脉冲相比,板选择性TSE序列的SNR增加了29%.
  • 平板选择性GRAPE脉冲显示出对B0场偏差的强度增加,并且比k-T-spoke脉冲更短.

结论:

  • 在关键的成像指标上,空间选择性的通用GRAPE脉冲在关键的成像指标上优于传统的k-T-spoke脉冲.
  • 这些新型脉冲是短的,坚固的,并且具有光谱选择性,提供了显著的优势.
  • 开发的脉冲有可能增强各种MRI应用,并加速7TMRI的临床采用.