Gradient phase and amplitude errors in atomic magnetic gradiometers for biomagnetic imaging systems.

The cross-axis projection error (CAPE) caused by residual magnetic fields has recently attracted widespread attention. In this study, we propose a more specific theoretical model and expand the CAPE in gradient measurements. We first report that differences in relaxation rate and residual magnetic field between optically pumped magnetometers (OPMs) introduce a significant error term in the output of OPM gradiometers, referred to as the gradient phase error. Furthermore, when the longitudinal field compensation is inadequate, the interaxial response interference of a single OPM is prominent, resulting in an amplitude distortion of the signal. This is further amplified in the gradiometer configuration, introducing the gradient amplitude error. Our experiments demonstrated that the efficacy of mitigating common-mode noise of OPM gradiometers was significantly impaired when existing the gradient errors. In addition, a simulation with a magnetoencephalography (MEG) system illustrated an induced source localization error of exceeding 2 cm, severely compromising the localization accuracy of OPM-MEG systems.

Vascular Smooth Muscle TRPV4 (Transient Receptor Potential Vanilloid Family Member 4) Channels Regulate Vasoconstriction and Blood Pressure in Obesity.

BACKGROUND: Vascular endothelium and smooth muscle work together to keep the balance of vasomotor tone and jointly maintain vascular homeostasis. Ca2+-permeable ion channel TRPV4 (transient receptor potential vanilloid family member 4) in endothelial cells regulates endothelium-dependent vasodilation and contraction in various states. However, how vascular smooth muscle cell TRPV4 (TRPV4SMC) contributes to vascular function and blood pressure regulation in physiological and pathologically obese condition has not been fully studied. METHODS: We generated smooth muscle TRPV4-deficient mice and developed diet-induced obese mice model and analyzed the role of TRPV4SMC in intracellular Ca2+ ([Ca2+]i) regulation and vasoconstriction. Vasomotor changes of mouse mesenteric artery were measured by wire, and pressure myography. [Ca2+]i were measured by fluo-4 staining. Blood pressure was recorded by telemetric device. RESULTS: Vascular TRPV4SMC played different roles in regulating vasomotor tone than endothelial TRPV4 due to their different features of [Ca2+]i regulation. Loss of TRPV4SMC attenuated U46619- and phenylephrine-induced contraction, suggesting its involvement in regulating vascular contractility. Mesenteric arteries from obese mice showed SMC hyperplasia, suggesting an increased level of TRPV4SMC. Loss of TRPV4SMC did not influence the development of obesity but protected mice from obesity-induced vasoconstriction and hypertension. In arteries deficient in SMC TRPV4, SMCs F-actin polymerization and RhoA dephosphorylation were attenuated under contractile stimuli. Moreover, SMC-dependent vasoconstriction was inhibited in human resistance arteries with TRPV4 inhibitor application. CONCLUSIONS: Our data identify TRPV4SMC as a regulator of vascular contraction in both physiological states and pathologically obese mice. TRPV4SMC contributes to the ontogeny of vasoconstriction and hypertension induced by TRPV4SMC over-expression in obese mice mesenteric artery.

In-situ measurement and cancellation of the light-shift in fiber-coupled atomic magnetometers.

In optical atomic magnetometers (AMs), the light-shift caused by the circularly polarized pumping beam have a significant impact on the response and is also one of the non-negligible sources of the noise. In this paper, we develop a novel method whereby utilizing the symmetry of the frequency response in an AM to measure and cancel the light-shift. Furthermore, we theoretically analyze and experimentally verify a rapid method of magnetic field compensation and the approach is convenient to measure and cancel of the light-shift. Moreover, the influence of intensity and frequency of the pumping beam is also investigated. The proposed method of in - situ measurement and cancellation of light-shift will be particularly profitable to other optical systems based on AMs.

Evaluation of optical parameters for a microminiature Rb vapor cell in a dual-beam SERF magnetometer.

In the spin-exchange relaxation-free (SERF) magnetometer of a perpendicular pump-probe configuration, the pump and probe beam characteristics significantly affect the performance. In this paper, an efficient evaluation of optical parameters to improve the sensitivity of a miniature magnetometer has been presented. We have determined the pump light's optimal intensity and wavelength through theoretical analysis and the zero-field resonance experiments. Chirp signals are applied to measure the optical rotations at different probe intensities and frequencies. Through theoretical and experimental analysis of noise source characterization under different beam intensities and wavelengths, we demonstrate that dual-beam magnetometer performance is mainly limited by photon shot noise. Based on the optimum pump and probe beam parameters, we demonstrate magnetic field sensitivity of 6.3 fT/Hz in an 87Rb vapor cell filled with nitrogen gas, with an active measurement volume of 3 × 3 × 3 mm3.

Rabi oscillation of spin-polarized rubidium in the spin-exchange relaxation-free regime.

The transient dynamics of atomic spins under oscillating and static magnetic fields have been studied in the spin-exchange relaxation-free (SERF) regime with a dual-beam configuration. The spin-relaxation rate can be accurately measured by detecting the transient response signal of the free induction decay (FID) process within several milliseconds. Leveraging this convenient method for measuring a large relaxation rate in a small cell volume, the dependence of the spin-relaxation rate on the probe intensity and ambient magnetic field was studied in the limit of low spin polarization. Moreover, by theoretical analysis of the dynamic evolution of the Rabi oscillation generated by a consecutive oscillating field and a small static magnetic field, we experimentally demonstrate that the amplitude of the Rabi oscillation is affected by the amplitude of the oscillating field in the SERF regime. According to the retrieved frequency of the FID signal and amplitude of relevant Rabi oscillation, the coil constants were 75.55 ± 0.78~nT/mA, 151.5 ± 0.9~nT/mA, and 116.6 ± 0.3~nT/mA along the x-, y-, and z-axes, respectively.

Optimized gas pressure of an Rb vapor cell in a single-beam SERF magnetometer.

We present a theoretical and experimental study of a single-beam spin-exchange relaxation-free magnetometer in 87Rb vapor cells under different nitrogen gas pressures. The spin relaxation rate is a key component to limit the magnetic sensitivity, and the zero-field resonance method was used to measure the spin relaxation rates of different alkali metal cells. Simultaneously, in a single-beam spin-exchange-relaxation-free (SERF) magnetometer, we demonstrated that the fundamental magnetic field sensitivity was also limited by the pumping light intensity. Based on our theoretical analysis and experimental results, we determined the optimal pumping light intensity and optimal gas pressure. We experimentally demonstrated that the magnetic field sensitivity was 8.89 fT/Hz in the single-beam configuration, with an active measurement volume of 3 × 3 × 3~mm3.

High-sensitivity operation of a single-beam atomic magnetometer for three-axis magnetic field measurement.

We demonstrate a single-beam atomic magnetometer (AM) capable of measuring a three-axis magnetic field with high-sensitivity, achieved by applying a small DC offset field and a high frequency modulation field. To satisfy the miniaturization demand of AMs, an elliptically polarized light detuned by 50 GHz from the resonance transition center is employed. The circularly polarized component is used to polarize the alkali-metal atoms, while the linearly polarized light is used to detect the dynamics of the polarized spin under a magnetic field. Based on theoretical analysis, parameters that significantly affect the performance are optimized, and a sensitivity of 20 fT/Hz1/2 in x-axis, 25 fT/Hz1/2 in y-axis, 30 fT/Hz1/2 in z-axis is achieved with a miniature 4 × 4 × 4 mm 87Rb vapor cell. Moreover, we also verify that the operation principle of AMs can be used to null background magnetic fields in-situ with isotropic compensation resolution of 6.7 pT, which provides an effectively precise method for zeroing ambient magnetic field. The high-sensitivity operating of an elliptically-polarized-laser-based magnetometer provides prospective futures for constructing a compact, low-cost AM, which is particularly applicable for non-invasive bio-magnetic imaging such as array-based magnetoencephalography (MEG) and magnetocardiography (MCG).

Transient dynamics of atomic spin in the spin-exchange-relaxation-free regime.

In this paper, we experimentally study transient dynamics of spin polarized atoms in the spin-exchange-relaxation-free (SERF) regime with a single-beam configuration. We pumped atoms with a weak detuning pumping beam, along with a sequence of magnetic field pulses orthogonal to the pumping beam were applied. The dynamics of atomic spin, which experiences Larmor precession under the perturbation of magnetic field, is detected by the transmitted pumping beam. Benefited from the long coherence time of atomic spin in the SERF regime, the dependence of precession frequency and decay rate, which is equal to the magnetic resonance linewidth of atomic spin, on magnetic fields is studied with the transient dynamics of atomic spin in the limit of low spin polarization. Moreover, we demonstrate that coil constants can be calibrated by analyzing the precession frequency of the transient dynamics of atomic spin. And the experimental results show that the coil constants are 114.25 ± 0.02 nT/mA and 114.12 ± 0.04 nT/mA in x- and y-axis, respectively. This method is particularly applicable to study the atomic spin dynamics and calibrate the coil constant in situ of a miniature single-beam SERF magnetometer.

IL10 hypomethylation is associated with the risk of gastric cancer.

Interleukin-10 (IL10), a pleiotropic cytokine secreted by type-2 helper (Th2) T cells, contributes to the oncogenic activation or inactivation of tumor-suppressor genes. The present study investigated whether hypomethylation of IL10 CpG island (CGI) was associated with the risk of developing gastric cancer (GC) and the prognosis of patients with GC. A fragment (hg18, chr1: 206945638-206945774) at the CGI of IL10 was selected for the present methylation assay. Quantitative methylation-specific PCR was used to evaluate the methylation of IL10 CGI in 117 tumor samples from patients with GC. The results demonstrated that IL10 CGI methylation was significantly lower in the tumor tissues compared with that in the paired adjacent non-tumor tissues (median percentage of methylated reference, 29.16 vs. 42.82%, respectively; P=4×10-8). Furthermore, results from receiver operating characteristic curve analysis identified a significant area under the curve of 0.706, with a sensitivity and a specificity of 77.8 and 58.1%, respectively, between cancer tissues and paired adjacent non-tumor tissues. Furthermore, the methylation of IL10 CGI was significantly associated with patients' age at diagnosis (r=-0.201; P=0.03). Subgroup analyses demonstrated that the association between IL10 CGI hypomethylation and the risk of GC was specific for patients with low differentiation (P=1×10-7) and Borrmann types III+IV (P=1×10-7). In addition, IL10 CGI hypomethylation was significantly associated with the risk of GC for patients without smoking history (P=3×10-7) or a family history of cancer (P=2×10-7). The results from Kaplan-Meier survival analysis demonstrated that IL10 CGI hypomethylation was associated with a significantly shorter overall survival of patients with GC (P=0.041). Similar results were identified for patients with GC who did not have smoking history (P=0.037) or a family history of cancer (P=0.049). The results from this study demonstrated that IL10 CGI hypomethylation may be considered as a potential biomarker for the diagnosis and prognosis of patients with GC in the Chinese population.

PTPN11 hypomethylation is associated with gastric cancer progression.

Protein tyrosine phosphatase non-receptor type 11 (PTPN11) encodes the tyrosine phosphatase SHP-2 that is overexpressed in gastric cancer (GC). In the present study, the association of PTPN11 methylation levels with the incidence of GC and its correlation with SHP-2 overexpression were investigated. The methylation levels of PTPN11 in tumor and adjacent normal tissues of 112 GC patients were assessed by quantitative methylation specific PCR (qMSP). The Cancer Genome Atlas (TCGA) public database was used to analyze the association between PTPN11 methylation and PTPN11 expression. Survival analyses were conducted in order to evaluate the prognostic value of PTPN11 methylation for GC. The results of the qMSP analysis indicated that the methylation levels of PTPN11 in GC tumor tissues were significantly decreased compared with those noted in the normal adjacent tissues (mean with standard deviation: 40.91±26.33 vs. 51.99±37.37, P=0.007). An inverse correlation between PTPN11 methylation levels and PTPN11 mRNA expression levels (P=4×10-6, r=-0.237) was noted. Subgroup analyses indicated that the association of PTPN11 hypomethylation with the incidence of GC was specific to male subjects (P=0.015), heavy drinking patients (P=0.019), patients with poor tumor differentiation (P=0.010) and patients with tumor node and metastasis (TNM) stage III+IV (P=0.008). Kaplan-Meier analyses and log-rank test suggested that PTPN11 hypomethylation was not associated with GC patient overall survival (P=0.605) and recurrence (P=0.485), although it could predict the recurrence of GC patients up to and including 60 years (≤60, P=0.049). The results indicated that PTPN11 levels were hypomethylated in GC patients. TCGA data analysis suggested that PTPN11 hypomethylation could cause an upregulation in the transcription levels of PTPN11. Although, this may explain the pattern of SHP-2 overexpression in GC, additional studies are required to verify this hypothesis. The association of PTPN11 hypomethylation with GC incidence may be specific to male patients, heavy drinking patients, patients with poor tumor differentiation and patients with TNM stage of III+IV. PTPN11 hypomethylation can be considered a biomarker for the recurrence of GC patients with an age of 60 years or lower.

Transplantation of VEGFl65-overexpressing vascular endothelial progenitor cells relieves endothelial injury after deep vein thrombectomy.

AIM: The purpose of this study was to explore the therapeutic efficacy of VEGF165-overexpressing vascular endothelial progenitor cells (EPCs) in post-thrombotic syndrome. MATERIALS AND METHODS: A thrombus model was developed to mimic the in-vivo setting, and adenovirus transfection was used to overexpress VEGF165 in EPCs. These cells were transplanted into the animal model, and their ability to relieve endothelial injury was evaluated using haematoxylin and eosin staining, immunohistochemistry and scanning electron microscopy. RESULTS: Ferric chloride was used to build rat models of the inferior vena cava thrombosis, and HEK 293A cells were used to amplify adenovirus that overexpresses VEGF165. EPCs were infected with adenovirus, and this was confirmed by fluorescence microscopy. Transplantation of VEGH165-overexpressing EPCs into injured endothelial sites led to faster repair of the post-thrombotic tunica intima than wild-type EPCs. CONCLUSION: Transplantation of VEGF165-overexpressing EPCs was found to promote repair of the tunica intima, thus improving rehabilitation after surgery.