Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis

Requested by the authors, the article entitled ＂Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis＂, published in Chinese Physics B, 2017, Vol. 26, Issue 9, Article No. 093301, has been withdrawn from the publication. The authors found that the axes in the rotating frame xy＇z are not all time-invariant, so Eq. （12） obtained from Eq. （11） is incorrect, and the conclusion is inaccurate.

Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis

A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.

Experimental Study on Double Resonance Optical Pumping Spectroscopy in a Ladder-Type System of ^(87)Rb Atoms

Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser beams acting on a rubidium vapor cell, the high resolution spectrum of 5S1/2 - 5P3/2 - 5D5/2 ladder-type transition of ST Rb atoms is obtained by monitoring the population of the 5S1/2 ground state. The dependence of the spectroscopy lineshape on the probe and coupling fields are comprehensively studied in theory and experiment. This research is helpful for measurement of fundamental physical constants by high resolution spectroscopy.

Double-resonance optical-pumping effect and laddertype electromagnetically induced transparency signal without Doppler background in cesium atomic vapour cell

In a Doppler-broadened ladder-type cesium atomic system （6S1/2 6P3/2-8S1/2）, this paper characterizes electro- magnetically induced transparency （EIT） in two different experimental arrangements, and investigates the influence of the double-resonance optical-pumping （DROP） effect on EIT in both arrangements. When the probe laser is weak, DROP is explicitly suppressed. When the probe laser is moderate, population of the intermediate level （6P3/2 FI = 5） is remarkable, therefore DROP is mixed with EIT. An interesting bimodal spectrum with the broad component due to DROP and the narrow part due to EIT has been clearly observed in cesium 6S1/2 F = 4-6P3/2 F^1= 5-8S1/2 F^11 = 4 transitions.

Off-resonant double-resonance optical-pumping spectra and their application in a multiphoton cesium magneto-optical trap

We present an investigation of double-resonance optical pumping （DROP） spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a coprop-agating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.

Reconstruction of vector static magnetic field by different axial NV centers using continuous wave optically detected magnetic resonance in diamond

We carried out a proof-of-principle demonstration of the reconstruction of a static vector magnetic field involving adjacent three nitrogen-vacancy(NV) sensors with corresponding different NV symmetry axes in a bulk diamond. By means of optical detection of the magnetic resonance(ODMR) techniques, our experiment employs the continuous wave(CW) to monitor resonance frequencies and it extracts the information of the detected field strength and polar angles with respect to each NV frame of reference. Finally, the detected magnetic field relative to a fixed laboratory reference frame was reconstructed from the information acquired by the multi-NV sensor.

Optical pumping and population transfer of nuclear-spin states of caesium atoms in high magnetic fields

Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti：sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the hyperfine Zeeman sublevels, which results from the collision-induced modification δa（S·I） of the hyperfine interaction of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different buffer-gas pressures. The experimental results show that high-field optical pumping and the small change δa（S · I） of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.

用数字示波器探究光磁共振实验中反常共振信号的机理

本文根据拟合得到的gF因子大小,确定了光磁共振实验中的反常共振信号;用数字示波器测量了反常共振射频信号的频谱,计算了反常共振射频信号各高次谐波的大小;通过线性拟合,得到了正常共振信号幅度与射频信号幅度的关系。利用此关系,计算了各高次谐波产生的反常共振信号大小,计算结果与测量值基本一致。频率计连接射频信号源后,射频信号波形和频谱发生明显变化,反常共振信号随着射频信号频谱的变化发生相应改变,进一步证明了反常共振信号由射频信号的高次谐波共振所引起。这些结果表明,用数字示波器探究光磁共振实验中反常共振信号的机理不仅可行,还能定量估算和预测射频信号波形对反常共振信号大小的影响。

基于SerialLite Ⅱ协议的磁共振采集数据传输系统设计

磁共振成像(MRI)是一种无创检测人体内部结构的技术,随着接收通道数量增多,产生的采集数据量越来越大,给快速成像带来了巨大的挑战。文中设计一种基于SerialLite Ⅱ协议的磁共振采集数据传输系统。系统功能主要由FPGA实现,分为数据缓存模块和数据传输模块两类,数据缓存模块基于双缓存区和状态机控制的乒乓操作,有效地解决了因数据量大而带来的读写冲突问题;数据传输模块基于FPGA建立SerialLite Ⅱ数据传输链路,实现了采集数据的光纤传输。通过仿真和实验验证了系统功能的正确性,表明其能够实现磁共振采集数据的高速稳定传输。

基于LF-NMR研究双孢菇远红外辅助热泵干燥过程中水分迁移规律及品质变化

为研究双孢菇远红外辅助热泵干燥过程中水分分布规律及品质变化,采用低场核磁共振及成像技术分别对干燥过程的双孢菇进行弛豫特性及质子密度成像分析,并研究干燥前、后双孢菇微观结构和品质的变化。结果表明:在热泵温度分别为45,55,65℃时,双孢菇到达干燥终点的时间分别为510,420,390 min。双孢菇的T2反演谱有3个不同的弛豫峰:T21(3~23 ms)、T22(25~155 ms)和T23(155~1084 ms),分别代表双孢菇中的结合水、不易流动水和自由水。干燥初期,T23左迁幅度很大,干燥后期,左迁幅度变小,随着干燥时间的延长,自由水的流动性降低。干燥结束时,T23对应的弛豫峰下降约99.8%,只剩下部分T21和T22对应的峰,说明自由水几乎被完全去除,双孢菇内仅剩结合水和少量不易流动水。低场核磁共振图像显示,65℃条件下,干燥360 min,水分基本被脱除,而55℃和45℃处理组分别在干燥390 min和450 min才基本脱除。双孢菇外侧的水分先被脱除,内部的水分向外迁移,并且温度越高,内部水分迁移速率越快。另外,65℃条件下的双孢菇的BI值分别比45℃和55℃条件下的BI低30.55%和22.69%,说明65℃更能维持双孢菇原有的色泽。65℃条件下干燥的双孢菇的抗坏血酸、总酚、总黄酮含量分别比干燥前下降84.62%,55.80%和36.78%,与45℃和55℃相比,65℃下双孢菇营养成分的损失最小。本研究表明低场核磁共振及成像技术为双孢菇干燥过程中水分的变化提供了直观的参考依据,也可为双孢菇的远红外辅助热泵干燥工艺优化干燥参数、提高产品质量提供理论参考。

FIRD-HPD方式对蓝莓干燥特性及品质的影响

为探究蓝莓在FIRD-HPD干燥方式下,内部水分含量及迁移状况随贮藏时间的变化规律,采用低场核磁共振(LF-NMR)及其成像技术(MRI),采集不同水分转换点干燥过程的蓝莓弛豫特性以及质子密度图像信息,分析其规律变化,并研究干燥前、后蓝莓品质的变化。结果表明:在水分转换点为30%,40%,50%时,蓝莓到达干燥终点的时间分别为480,420min和360 min。蓝莓的T2反演谱有3个不同的弛豫峰:T21(0.01~10 ms)结合水、T22(10~100 ms)不易流动水和T23(100~1000 ms)自由水。自由水(T23)和不易流动水(T22)向弛豫时间短的方向迁移,在干燥后期,结合水成为蓝莓中主要水分状态,自由水完全消失。基于MRI技术得到不同干燥方式各干燥阶段的磁共振成像,质子信号随干燥进程逐渐减小。LF-NMR和MRI技术可很好地监测干燥过程中动态水分分布和迁移变化。另外,在40%水分转换点联合远红外热泵干燥处理下,蓝莓果干色泽、营养品质等指标均优于30%和50%的水分转换点联合远红外热泵干燥方式。综合考量后,联合红外干燥水分转换点设置为40%是加工蓝莓果干的最优选择。

快速响应的NV色心微波传感器实现及测量

高精度微波快速测量技术是电磁频谱分析监测的核心,微波测量技术为微波传感器的高精度测量提供了可能。通过建立NV色心空间磁场能级响应频率精密调谐模型,结合NV色心光学宽场成像技术,实现了高精度、响应快可调的微波测量。首先,通过连续光探测磁共振(ODMR)技术,结合宽场成像技术,通过像素级磁场强度-微波频率转化关系,实现宽场成像的微波测量;进而将连续扫频技术转变为施加定频进行检测,通过同步监测频点不同的响应特性,验证了测试结果的有效性。以上结果为高精度固态量子频谱分析仪、高瞬时带宽频谱微波传感器提供了重要技术基础。

氢质子MR波谱成像评估轻中度甲状腺相关性眼病视放射的微代谢改变

目的应用氢质子MRI波谱成像(^(1)H-MRS)技术探讨轻、中度甲状腺相关性眼病(TAO)视放射(OR)代谢物浓度的改变,探究甲状腺异常性视神经病(DON)的发病机理。方法本研究为前瞻性,研究对象为2020年11月—2021年7月来我院就诊的眼科门诊(22例)及内分泌科住院(12例)的轻、中度TAO患者34例及同期向社会招募的15例健康志愿者[健康对照组(HC组)]。根据纳入和排除标准,纳入TAO患者33例。根据临床活动评分(CAS)将TAO患者分为非活动性组14例、活动性组19例,根据病程分为慢性组(病程>6个月)17例、急性组(病程≤6个月)16例。研究采用用3.0 T MR设备、单体素^(1)H-MRS技术,对研究者行轴面T1-反转恢复序列、水抑制点分辨频谱脉冲序列扫描;同时测量TAO患者的双侧突眼度,检测血清游离甲状腺激素(FT3、FT4)、促甲状腺激素(TSH)、抗甲状腺激素受体抗体(TRAb)、抗甲状腺过氧化物酶抗体(TPOAb)、抗甲状腺球蛋白抗体(TgAb)。采用单因素方差分析对TAO非活动性组、活动性组及HC组之间及TAO慢性组、急性组及HC组之间年龄及^(1)H-MRS检测的代谢物[谷氨酰胺(Gln)、谷氨酸(Glu)、肌醇(mI)等]进行比较。采用χ^(2)检验比较TAO组和HC组的性别差异。使用Spearman相关分析对TAO患者突眼程度、血清检测指标与^(1)H-MRS检测的代谢物浓度之间的相关性进行分析。结果与HC组和活动性组相比,非活动性组患者OR中mI水平显著减低(F=3.29,P<0.05)。与HC组相比,慢性组患者OR中Gln水平升高(F=3.31,P<0.05)。在TAO各组中(非活动性组、活动性组,慢性组、急性组)突眼度均与TSH水平呈正相关,(r值分别为0.373,0.411,0.347,0.489;P均<0.05)。结论单体素^(1)H-MRS能有效评估TAO患者OR微代谢的改变。

局限性硬皮病诊断技术研究进展

局限性硬皮病(LS)是一种主要影响皮肤、皮下脂肪和深层组织的自身免疫性疾病,可能导致严重的功能障碍和外观受损。及时准确的诊断对于患者的治疗和管理至关重要,但目前LS在诊断方面尚存在困难。本文综述了LS诊断领域的最新进展,包括高频超声、磁共振成像、光学相干断层扫描及分子和基因检测等。这些技术提高了诊断的精确性和即时性。高频超声能够精确评估皮肤病变;磁共振成像有助于深层组织受累的评估;光学相干断层扫描和皮肤镜揭示皮肤微小结构变化;分子和基因检测为理解疾病机制及个体化治疗提供新视角。尽管新技术的应用受到成本和设备普及度的限制,但其在改善诊断流程、提供个性化治疗方面有着显著的潜力。未来研究需要进一步探讨这些技术与传统方法的整合及其在LS不同亚型和疾病阶段中的应用。

A polarized^(3)He system based on metastability-exchange optical pumping

Hyperpolarized^(3)He nuclei have emerged as a significantly important approach in quantum precision measurement techniques,with extensive applications in fundamental physics,magnetometry,metrology,and beyond.In this study,we report on the design and implementation of a^(3)He polarization system at the China Mianyang Research Reactor(CMRR),utilizing the metastabilityexchange optical pumping(MEOP)method.We employed a Merritt coil system consisting of four square coils to furnish a uniform holding field.We deployed a 2 W fiber laser to pump the metastable^(3)He atoms and conducted free induction decay(FID)detection of the polarized^(3)He nuclei using both pickup coil and optical methods.For the optical method,we used a50 m W linearly polarized distributed Bragg reflector(DBR)laser as the probe.We applied transverse light absorption polarimetry to measure the absolute nuclear polarization of the ground-state^(3)He.We have developed cell fabrication capabilities at the CMRR,and cells at various pressures ranging from 100 to 1000 Pa have been fabricated and evaluated.For a typical borosilicate cell with 100 Pa pressure,the absolute polarization is measured as Pn≈70%,and the transverse relaxation time is estimated as T2≈0.5 s.Moreover,we constructed a few aluminosilicate cells,each carefully filled with pure^(3)He at a pressure of 100 Pa.Subsequently,we conducted a comprehensive evaluation of their performance in the context of MEOP.

A Prediction Model for Detecting Dysthyroid Optic Neuropathy Based on Clinical Factors and Imaging Markers of the Optic Nerve and Cerebrospinal Fluid in the Optic Nerve Sheath

Objective This study aimed to develop and test a model for predicting dysthyroid optic neuropathy(DON)based on clinical factors and imaging markers of the optic nerve and cerebrospinal fluid(CSF)in the optic nerve sheath.Methods This retrospective study included patients with thyroid-associated ophthalmopathy(TAO)without DON and patients with TAO accompanied by DON at our hospital.The imaging markers of the optic nerve and CSF in the optic nerve sheath were measured on the water-fat images of each patient and,together with clinical factors,were screened by Least absolute shrinkage and selection operator.Subsequently,we constructed a prediction model using multivariate logistic regression.The accuracy of the model was verified using receiver operating characteristic curve analysis.Results In total,80 orbits from 44 DON patients and 90 orbits from 45 TAO patients were included in our study.Two variables(optic nerve subarachnoid space and the volume of the CSF in the optic nerve sheath)were found to be independent predictive factors and were included in the prediction model.In the development cohort,the mean area under the curve(AUC)was 0.994,with a sensitivity of 0.944,specificity of 0.967,and accuracy of 0.901.Moreover,in the validation cohort,the AUC was 0.960,the sensitivity was 0.889,the specificity was 0.893,and the accuracy was 0.890.Conclusions A combined model was developed using imaging data of the optic nerve and CSF in the optic nerve sheath,serving as a noninvasive potential tool to predict DON.

Vector magnetometry in zero bias magnetic field using nitrogen-vacancy ensembles

The application of the vector magnetometry based on nitrogen-vacancy(NV)ensembles has been widely investigatedin multiple areas.It has the superiority of high sensitivity and high stability in ambient conditions with microscale spatialresolution.However,a bias magnetic field is necessary to fully separate the resonance lines of optically detected magneticresonance(ODMR)spectrum of NV ensembles.This brings disturbances in samples being detected and limits the rangeof application.Here,we demonstrate a method of vector magnetometry in zero bias magnetic field using NV ensembles.By utilizing the anisotropy property of fluorescence excited from NV centers,we analyzed the ODMR spectrum of NVensembles under various polarized angles of excitation laser in zero bias magnetic field with a quantitative numerical modeland reconstructed the magnetic field vector.The minimum magnetic field modulus that can be resolved accurately is downto~0.64 G theoretically depending on the ODMR spectral line width(1.8 MHz),and~2 G experimentally due to noisesin fluorescence signals and errors in calibration.By using 13C purified and low nitrogen concentration diamond combinedwith improving calibration of unknown parameters,the ODMR spectral line width can be further decreased below 0.5 MHz,corresponding to~0.18 G minimum resolvable magnetic field modulus.

继发性牙根纵裂诊断的研究进展

牙根纵裂是一种源自牙根的纵向裂纹,可发生在活髓牙和根管治疗后牙齿,是病因复杂、预后较差的牙体硬组织疾病。发生于牙髓治疗后的牙根纵裂称为继发性牙根纵裂(secondary vertical root fracture,SVRF),对SVRF的诊断,应结合临床体征(如疼痛、肿胀、牙齿松动、位于牙龈边缘附近的窦道和深而窄的孤立牙周袋)和根尖片(如牙周膜增宽、垂直骨丧失和根周骨丧失、根周“晕圈状”或“J”形的透射影)进行综合判断。对疑似牙根纵裂的牙齿,应通过锥形束CT(cone⁃beam computed tomography,CBCT)等三维影像学辅助诊断,如CBCT显示牙根上的折裂线以及颊侧或舌侧骨板缺损;优化设置CBCT参数,如选用小视野CBCT、增强染料辅助的应用、使用金属伪影还原工具(metal artifact reduction,MAR)等方法提高CBCT诊断SVRF的精确度。使用多种影像技术可对不同宽度的裂纹进行检测,如核磁共振成像(magnetic resonance imaging,MRI)中表现为异常的高强度信号;使用数字减影技术(digital subtraction radiography,DSR)进行图像处理后出现的黑色线状区域;不同宽度的裂纹在光学相干断层扫描(optical coherence tomography,OCT)可表现为高亮度线或暗区。人工智能(artificial intelligence,AI)诊断技术和预测模型也是SVRF诊断的辅助手段。通过各种无创手段仍然无法确诊的SVRF病例,可通过根管内直视和翻瓣手术中直视发现SVRF。

基于玻色凝聚^(87)Rb原子气体相位Ramsey干涉的磁场探测

基于玻色凝聚原子气体的磁场探测可兼顾高灵敏度和高空间分辨率.利用一维光晶格中玻色凝聚^(87)Rb原子气体F=1,m_(F)=1→F=2,m_(F)=-1(F为原子总角动量的量子数,m_(F)为F能级的磁量子数)的双光子跃迁,已实现基于相位Ramsey干涉的精密磁场探测.本研究利用交叉光阱中玻色凝聚^(87)Rb原子气体F=1,m_(F)=1→F=2,m_(F)=0的单光子跃迁,实验研究了频域Ramsey干涉、时域Ramsey干涉及相位Ramsey干涉,并基于相位Ramsey干涉评估了静态磁场测量的灵敏度和空间分辨率.通过对比上述3种Ramsey干涉的实验结果,发现相位Ramsey干涉可有效避免频域Ramsey干涉条纹的畸变和时域Ramsey干涉的退相干效应,从而提高静态磁场测量的灵敏度和准确度.在无磁屏蔽环境中,利用体积为(1.31±0.03)×10^(-9)cm^(3)的玻色凝聚^(87)Rb原子气体,获得了130 nT/√Hz的灵敏度,通过压缩原子气体制备时间和提高信号积累时间,灵敏度有望得到进一步提升.