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Acoustic liners are the most commonly used dissipative muffler for aero-engines but remain a challenge to design a broadband acoustic liner under the grazing flow. In this work, a novel neck-embedded meta-liner is proposed for the broadband sound-absorbing under the grazing flow with a wide speed range. The meta-liner is composed of many neck-embedded Helmholtz Resonators, and the idea of bending the subsequent cavity is introduced to improve low-frequency sound absorption performance. The acoustic impedance model of the meta-liner with neck-embedded slit is first detailly established by analyzing the acoustic characteristics of the equivalent elliptical pipe and using the matrix transfer method. Then by designing the local coupling between channels, efficient broadband impedance modulation and broadband matching with air impedance under grazing flow conditions are realized. The proposed meta-liner exhibits the excellent sound attenuation capacity in the frequency domain of 500–3000 Hz under the grazing flow speeds from 0 m s−1 to 98 m s−1 and the sound absorption performance is greatly boosted compared with the traditional Double- Degree-Of-Freedom liner. Features mentioned above have been verified numerically and in a series of comparative experiments. Besides, the thickness of the meta-liner is only 50 mm. Our work provides a possible design reference for the new generation of acoustic liners and has potential applications in noise reduction engineering. [ABSTRACT FROM AUTHOR]

Objective: To explore the clinical feasibility of applying deep learning (DL) reconstruction algorithm in low-dose thin-slice liver CT examination of healthy volunteers by comparing the reconstruction algorithm based on DL, filtered back projection (FBP) reconstruction algorithm and iterative reconstruction (IR) algorithm., Methods: A standard water phantom with a diameter of 180 mm was scanned, using the 160 slice multi-detector CT scanning of United Imaging Healthcare, to compare the noise power spectrums of DL, FBP and IR algorithms. 100 healthy volunteers were prospectively enrolled, with 50 assigned to the normal dose group (ND) and 50 to the low dose group (LD). IR algorithm was used in the ND group to reconstruct images, while DL, FBP and IR algorithms were used in the LD group to reconstruct images. One-way analysis of variance was used to compare the liver CT values, the liver noise, liver signal-to-noise ratio (SNR), contrast noise ratio (CNR) and figure of merit (FOM) of the images of ND-IR, LD-FBP, LD-IR and LD-DL. The Kruskal-Wallis test was used to analyse subjective scores of anatomical structures., Results: The DL algorithm had the lowest average peak value of noise power spectrum, and its shape was similar to that of medium-level IR algorithm. Liver CT values of ND-IR, LD-FBP, LD-IR and LD-DL did not show statistically significant difference. The noise of LD-DL was lower than that of LD-FBP, LD-IR and ND-IR ( P <0.05), and the SNR, CNR and FOM of LD-DL were higher than those of LD-FBP, LD-IR and ND-IR ( P <0.05). The subjective scores of anatomical structures of LD-DL did not show significant difference compared to those of ND-IR ( P >0.05), and were higher than those of LD-FBP and LD-IR. The radiation dose of the LD group was reduced by about 50.2% compared with that of the ND group., Conclusion: The DL algorithm with noise shape similar to the medium iterative grade IR commonly used in clinical practice showed higher noise reduction ability than IR did. Compared with FBP, the DL algorithm had smoother noise shape, but much better noise reduction ability. The application of DL algorithm in low-dose thin-slice liver CT of healthy volunteers can help achieve the standard image quality of liver CT., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Objective: To evaluate the noise reduction effect of deep learning-based reconstruction algorithms in thin-section chest CT images by analyzing images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and deep learning image reconstruction (DLIR) algorithms., Methods: The chest CT scan raw data of 47 patients were included in this study. Images of 0.625 mm were reconstructed using six reconstruction methods, including FBP, ASIR hybrid reconstruction (ASIR50%, ASIR70%), and deep learning low, medium and high modes (DL-L, DL-M, and DL-H). After the regions of interest were outlined in the aorta, skeletal muscle and lung tissue of each group of images, the CT values, SD values and signal-to-noise ratio (SNR) of the regions of interest were measured, and two radiologists evaluated the image quality., Results: CT values, SD values and SNR of the images obtained by the six reconstruction methods showed statistically significant difference ( P <0.001). There were statistically significant differences in the image quality scores of the six reconstruction methods ( P <0.001). Images reconstruced with DL-H have the lowest noise and the highest overall quality score., Conclusion: The model based on deep learning can effectively reduce the noise of thin-section chest CT images and improve the image quality. Among the three deep-learning models, DL-H showed the best noise reduction effect., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Objective: To compare the noise reduction performance of conventional filtering and artificial intelligence-based filtering and interpolation (AIFI) and to explore for optimal parameters of applying AIFI in the noise reduction of abdominal magnetic resonance imaging (MRI)., Methods: Sixty patients who underwent upper abdominal MRI examination in our hospital were retrospectively included. The raw data of T1-weighted image (T1WI), T2-weighted image (T2WI), and dualecho sequences were reconstructed with two image denoising techniques, conventional filtering and AIFI of different levels of intensity. The difference in objective image quality indicators, peak signal-to-noise ratio (pSNR) and image sharpness, of the different denoising techniques was compared. Two radiologists evaluated the image noise, contrast, sharpness, and overall image quality. Their scores were compared and the interobserver agreement was calculated., Results: Compared with the original images, improvement of varying degrees were shown in the pSNR and the sharpness of the images of the three sequences, T1W1, T2W2, and dual echo sequence, after denoising filtering and AIFI were used (all P <0.05). In addition, compared with conventional filtering, the objective quality scores of the reconstructed images were improved when conventional filtering was combined with AIFI reconstruction methods in T1WI sequence, AIFI level≥3 was used in T2WI and echo1 sequence, and AIFI level≥4 was used in echo2 sequence (all P <0.05). The subjective scores given by the two radiologists for the image noise, contrast, sharpness, and overall image quality in each sequence of conventional filtering reconstruction, AIFI reconstruction (except for AIFI level=1), and two-method combination reconstruction were higher than those of the original images (all P <0.05). However, the image contrast scores were reduced for AIFI level=5. There was good interobserver agreement between the two radiologists (all r >0.75, P <0.05). After multidimensional comparison, the optimal parameters of using AIFI technique for noise reduction in abdominal MRI were conventional filtering+AIFI level=3 in the T1WI sequence and AIFI level=4 in the T2WI and dualecho sequences., Conclusion: AIFI is superior to filtering in imaging denoising at medium and high levels. It is a promising noise reduction technique. The optimal parameters of using AIFI for abdominal MRI are Filtering+AIFI level=3 in the T1WI sequence and AIFI level=4 in T2WI and dualecho sequences., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Objective: To evaluate the diagnostic value of 3.0T time-of-flight MR angiography with sparse undersampling and iterative reconstruction (TOFu-MRA) for unruptured intracranial aneurysms (UIAs) on the basis of using digital subtraction angiography (DSA) as the reference standard., Methods: A total of 65 patients with suspected UIAs were prospectively enrolled and all patients underwent TOFu-MRA and DSA. Relying on DSA as the reference standard, the sensitivity (SEN), specificity (SPE), positive predictive value (PPV) and negative predictive value (NPV) of using TOFu-MRA in UIA diagnosis were calculated, and the inter-observer agreement between two doctors was determined. Comparison of maximum intensity projection (MIP) and volume rendering (VR) image datasets was made to evaluate the agreement between DSA results and TOFu-MRA in the measurement of UIA morphological parameters, including the neck width (D neck ), height (H) , and width (D width ) of UIAs., Results: The study covered 55 UIAs from 46 patients. The SEN, SPE, PPV and NPV of the two doctors using TOFu-MRA in UIA diagnosis were as follows: (95.7%, 95.7%), (94.7%, 94.7%), (97.8%, 97.8%) and (90.0%, 90.0%), respectively for patient-based assessment; (96.4%, 94.5%), (94.7%, 94.7%), (98.1%, 98.1%) and (90.0%, 85.7%), respectively, for aneurysm-based assessment. There is a strong inter-observer agreement (Kappa=0.93 for patient-based assessment and 0.96 for aneurysm-based assessment) between the two doctors. Moreover, Bland-Altman analysis showed that more than 95% points fell within the limits of agreement (LoA), suggesting strong agreement between the two examination methods for the measurement of UIAs morphological parameters., Conclusion: TOFu-MRA showed good diagnostic efficacy for UIAs and the results were in good agreement with those of DSA, the reference standard, for assessing UIA morphological parameter. TOFu-MRA can be used as a first choice for noninvasive diagnostic evaluation of UIAs., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Obstract Purpose "One-stop" CT myocardial perfusion imaging (CT-MPI) was compared with cardiac magnetic resonance(CMR) to investigate its application value in evaluating patients with severe coronary artery stenosis. Methods Fifty patients with coronary artery stenosis≥90% of at least one major coronary arteries comfirmed by coronary angiography (CAG) in the department of cardiology in our hospital, who referred for coronary artery stent implantation were prospectively enrolled. All the patients underwent "One-stop" CT-MPI within a week before surgery, among which 22 patients underwent CMR examination simultaneously. The postprocessing software Ziostation2 was used to obatin and compare the perfusion parameters of patients with normal and perfusion defect myocardium, including blood flow (BF), blood volume (BV), peak time (TTP), and mean transit time (MTT). Pearson correlation analysis was used to compare the correlation of relative perfusion parameters (defect/normal myocardium) between CT and CMR. Bland-Altman analysis was used to analyze the consistency between CT and CMR in left ventricular (LV) function parameters measurements. Results Compared with normal myocardium, BV and BF of perfusion defect myocardium were significantly decreased, while MTT and TTP were significantly prolonged (all P < 0.05). The rBV, rBF, rMTT and rTTP were medium to high positive correlated between CT and CMR ( r =0.685, 0.641, 0.871, 0.733, respectively, all P < 0.05). Bland-Altman analysis showed that 95% (21/22) points were within the 95% limits of agreement (LoA), suggesting the LV function parameters measurements between two methods were highly consistent. Conclusion "One-stop" CT-MPI can simultaneously obtain the information about coronary anatomy, myocardial perfusion and LV function. It is of great value in the evaluation of patients with severe coronary artery stenosis, with shorter scan time and less contraindications compared with CMR., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Science Edition).)

Objective: To determine the value of automated detection in computed tomography angiography (CTA) for cases with greater than 70% coronary stenosis., Methods: Fifty-seven patients who had both coronary CTA and digital subtraction angiography (DSA) were retrospectively recruited in this study. The patients were categorized into two groups using a cutoff value of 70% stenosis in DSA. The AW4.6 software was used to estimate the diameter and square values from the data obtained from CTA. The sensitivity (SE), specificity (SPE), positive predictive value (PPV) and negative predictive value (NPV) of the automated CTA estimations were calculated., Results: A total of 178 vessels from the 57 patients were analyzed. The automated CTA estimations had moderate to high levels of agreements ( Kappa value: 0.716-0.804, P < 0.001) with the DSA diagnoses, compared with low to moderate levels of agreements ( Kappa value: 0.385-0.533, P < 0.001) in manual interpretations. The square estimations generated high SE (100%) and NPV (100%) for patient diagnoses ( P < 0.016 7 vs. manual interpretations). The diameter estimations generated high SPE (90.48%) and PPV (94.12%) for patient diagnoses ( P < 0.016 7, vs. manual interpretations). Similarly, high SE (96.92%) and NPV (97.89%) were found for square estimations in vessel diagnoses, while high SPE (94.69%) and PPV (90.16%) were found for diameter estimations in vessel diagnoses., Conclusions: Both automated diameter and square algorithms have high accuracy for diagnosing patients with greater than 70% coronary artery stenosis. The AW4.6 can improve the detection of severe stenosis that needs stent interventions., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Science Edition).)

Objective: To determine consistencies between MR perfusion weighted imaging (PW-MRI) and CT perfusion imaging (CTP) in assessing hemodynamics of patients with moyamoya disease (MMD)., Methods: Images of PWI and CTP scan [including the map of cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP), and mean transmit time (MTT)] of 24 MMD patients diagnosed by digital subtraction angiography(DSA) or time of flight-MR angiography (TOF-MRA) were obtained in the week before vascular reconstruction operations. Relative perfusion parameters (rCBF, rCBV, rMTT, rTTP) at the operative side within the middle cerebral artery territory and cerebellar hemisphere were compared with those of 17 patients without hypoperfusion and cerebrovascular disease using independent sample t test. Paired t test and Pearson correlation analyses were performed between the results of PWI-MRI and CTP., Results: Different parameters were found in the MMD patients compared with the controls ( P <0.05). The parameter results of PWI-MRI differed from those of CTP, but they were strongly correlated., Conclusion: Both PWI-MRI and CTP can detect the area and degree of hypoperfusion of MMD patients., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Science Edition).)

The relationship between ambient relative humidity H and the position shift of a spectral line was investigated both experimentally and theoretically. An echelle-based ICP emission spectrometer equipped with a CID detector was used for experimental verification of the derived model. The shift of a spectral line is quantitatively described by two defined spectral shift functions: delta lambda x(x, lamda, H) (in the x direction of the CID detector) and delta lambda y(y, lambda, H) (in the y direction of the CID detector). Experimental results indicate that delta lamda x(x, lambda, H) does not change with a variation in ambient relative humidity, but delta lamda y(y, lambda, H) does. A spectral shift equation, i.e., an empirical second-order polynomial equation, can be used to describe the relationship between delta lamda y(y, lambda, H) and H. Based on the classical dipole model, classical mechanics and electrodynamics the empirical spectral-shift equation involving delta lambda y(y, lambda, H) and H was theoretically deduced. The theoretical result is in good agreement with the experimental findings. The theoretical results indicate that the coefficients of the empirical spectral-shift equation are related to the basic physical parameters of materials and the geometric configuration of the echelle CID ICP-AES, and also provide physical meaning to the coefficients of the empirical shift equation obtained experimentally.

The present review covers the latest progress in instruments and methodology of analytical atomic spectrometry in the areas, such as atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), atomic fluorescence spectrometry (AFS), laser induced breakdown spectrometry (LIBS) and atomic mass spectrometry (AMS). The emphasis has focused in the fields of food, medicine and their relevant. The Lab-on-chips and microplasmas are emerged in recent years, which have facilitated the development of miniaturization of analytical atomic instruments. The applications of laser and hyphenaed techniques continue in popularity for speciation studies.

Objective: To identify antithrombin III (AT-III) gene mutation and polymorphisms in pregnant women and parturients with cerebral venous thrombosis (CVT) using denaturing high-performance liquid chromatography (DHPLC)., Methods: The genomic DNA was extracted from the blood samples of 50 pregnant women and parturients with CVT and 52 matched healthy women for molecular analysis using a PCR/DHPLC assay followed by DNA sequence analysis. Ten primer pairs were designed for amplifying the AT- III promoter region and exons 1-6 including the exon/intron boundaries. A rapid screening assay based on DHPLC was established to screen the mutation and polymorphisms of AT- III gene., Results: Six abnormal peaks were detected in 40 of the patients by DHPLC. Direct DNA sequencing was performed on representative samples detected by DHPLC profiling. One pathogenic heterozygous G13328A missense mutation in exon 6, and a novel silent mutation in exon 4+243 G>A were identified. Six single nucleotide polymorphism (SNP) sites were found, including 4 previously reported ones in the SNP library and two were novel SNP sites. An abnormal peak was detected in the control group by DHPLC., Conclusion: DHPLC allows automated and rapid high-throughput detection of AT- III gene mutation and polymorphisms in the clinical setting and prenatal diagnosis. Our findings suggested that AT- III gene mutation, as well as its polymorphisms, contributes to the occurrence of CVT in pregnant women and parturients.

The content of this review covers atomic absorption spectroscopy, atomic fluorescence spectroscopy, atomic emission spectroscopy, inductively coupled plasma mass spectroscopy, sampling systems and preconcentration systems of spectrochemical analysis, speciation of inorganic elements, process analytical chemistry, and sensors of inorganic elements.

The trace elements Si, Al, Fe, Ca, Mn, Mg, and Cl in the K2Cr2O7 produced by chromate cleaner production were determined by a sequential inductively coupled plasma spectrometer in this paper. Matrix effect was studied and eliminated through matrix matching. The analytical conditions for the elements were optimized. Incident power of the RF generator was 0.95 kW. Pressure of carrier gas flow was 0.13 MPa, and its flow rate was 1.2 L x min(-1). Auxiliary gas flow rate was 0.2 L x min(-1). The element Cl was indirectly determined by the method of AgCl precipitation. The ion Cl- can be completely precipitated in 6% nitric acid system, and then determined after keeping the solution at 50 degrees C for two hours. The recoveries of the studied impurities range from 95% to 104%, and the relative standard deviations are lower than 4% (n = 10). Detection limits of these impurities are in a range 0.0001%-0.00001% (w/w). The analytical results of random samples agree well with the results using the standard-adding method, and the relative error varies from -4.27% to +5.26%. The developed method has been applied to the determination of impurities in K2Cr2O7 product with satisfactory results.

One-dimension wavelength shift of atomic spectral lines in 0-800 nm spectral range was observed, and the relationships between temperature, humidity, pressure, and the magnitudes of wavelength shift of the atomic spectral lines were found, which were expressed as some polynomial equations in this paper. The universality of these wavelength shift equations (above mentioned polynomial equations) is primarily proved experimentally. The nonlinear relationship between the half-width of spectra lines and temperature was also found. Based on these equations, an intelligent wavelength calibration device (IWC) was designed in the author's lab. The analytical results of samples indicate that IWC is useful and effective.

Genetic algorithm (GA) is used in automatic qualitative analysis by a sequential inductively coupled plasma spectrometer (ICP-AES) and a computer program is developed in this paper. No any standard samples are needed, and spectroscopic interferences can be eliminated. All elements and their concentration ranges of an unknown sample can be reported. The replication rate Pr, crossover rate Pc, and mutation rate of the genetic algorithm were adjusted to be 0.6, 0.4 and 0 respectively. The analytical results of GA are in good agreement with the reference values. It indicates that, combined with the intensity information, the GA can be applied to spectroscopic qualitative analysis and expected to become an effective method in qualitative analysis in ICP-AES after further work.