Identification of line-source transfer mobility and force density by ground acceleration measurements.

Ground-borne vibration caused by railway traffic has been a research concern due to its possible side effects on nearby residences. The force density and line-source mobility can effectively characterize the generation and transmission of train-induced vibrations, respectively. This research proposed a frequency-domain method for identifying the line-source transfer mobility and force density using measured vibrations at the ground surface, which was on the basis of the least-square method. The proposed method was applied to a case study at Shenzhen Metro in China, where a total of seven fixed-point hammer impacts with 3.3 m equal intervals were used to represent the train vibration excitations. Line-source transfer mobility of the site and force density levels of the metro train were identified, respectively. Causes for different dominant frequencies can be traced by separating the dynamic characteristics of vibration excitation and transmission. It was found in the case study that at a location 3 m away from the track, the peak at 50 Hz was caused by excitations, while that at 63 Hz was attributed to transmission efficiency related to the soil properties. Subsequently, numerical validations of the fixed-point loads' assumption and identified force density levels were carried out. Good comparisons between numerically predicted and experimentally identified force density levels indicated the feasibility of the proposed method. At last, the identified line-source transfer mobility and force density levels were applied to the forward problem, i.e., making predictions of train-induced vibrations. The predicted ground and structural vibrations at different locations were compared to corresponding measurements, with good agreement, which experimentally validated the identification method. The identification results of the case study can be employed by similar railway systems as a good reference.

The impacts of transcatheter occlusion for congenital atrial septal defect on atrial volume, function, and synchronicity in children: a three-dimensional echocardiography study.

OBJECTIVE: To evaluate the impacts of transcatheter closure for atrial septal defect (ASD) on the atria. METHODS: Thirty-four patients with ASD undergoing transcatheter occlusion were recruited in the study, and 34 patients undergoing surgical operation and 34 healthy children were age-matched as controls. A real time three-dimensional (RT3DE) echocardiography was used to measure the volume, function, and synchronicity of the atria. RESULTS: There was no difference in the atrial volume and function between the transcatheter occlusion group and healthy control group (P > 0.05). However, the parameters reflecting the atrial asynchrony were larger in the transcatheter occlusion group (P < 0.05). Compared to the surgical repair group, the transcatheter occlusion group had smaller maximum volume of the left atrium (21.0 +/- 5.2 ml/m(2) vs 24.3 +/- 5.8 ml/m(2), P = 0.01), smaller total emptying volume of the left atrium (12.7 +/- 4.3 ml/m(2) vs 15.1 +/- 3.8 ml/m(2), P = 0.014), smaller total emptying volume of the right atrium (13.5 +/- 5.2 ml/m(2) vs 16.1 +/- 4.7 ml/m(2), P = 0.029), and larger atrial systolic asynchrony indices. CONCLUSIONS: An atrial asynchrony is observed in patients with transcatheter closure of ASD, although little negative impacts on the atrial volume and function are demonstrated, which deserves more attention during follow-up of this specific population.

Value of real-time 3-dimensional echocardiography sectional diagnosis in complex congenital heart disease evaluated by receiver operating characteristic analysis.

OBJECTIVE: We sought to evaluate the value of real-time 3-dimensional (3D) echocardiography (RT-3DE) in the pathologic morphology of complex congenital heart disease (CHD) using receiver operating characteristic (ROC) analysis. METHODS: Thirty patients with complex CHD were examined by 2-dimensional echocardiography (2DE) and RT-3DE. Their diagnoses of pathologic morphology were made by 3 echocardiographers blinded to clinical data. Their value was evaluated by ROC analysis using a 5-point categorical scale in major cardiovascular structures and spatial relationships among complex CHD. RESULTS: Compared with surgical findings, there were 75.6% of the definitely correct in RT-3DE and 64.4% in 2DE. ROC curve for RT-3DE was located left-superior to that for 2DE, and the area under ROC curve for RT-3DE (A = 0.96) was higher than that for 2DE (A = 0.90). There was significant difference between them by the method of Z test (Z = 2.64, P = .0083). CONCLUSIONS: With the spatial 3D display of cardiovascular structural malformations, RT-3DE, coupled with conventional Doppler 2DE, may add information on complex CHD.

[The study of vascular lesion using ultrasound in children with a history of Kawasaki disease].

OBJECTIVE: To explore the endothelial function, carotid artery stiffness index and carotid intima-media thickness in children with a history of Kawasaki disease (KD). METHODS: A cohort of 204 children was studied, which comprised 51 patients with Kawasaki disease with coronary artery lesion (CAL group), 50 patients with Kawasaki disease with normal coronary arteries (normal coronary arteries group), and 103 healthy age matched children (control group). Their systemic blood pressure, fasting cholesterol concentrations, flow-mediated dilation (FMD) of the brachial artery, carotid artery stiffness index and carotid intima-media thickness (IMT) were compared. RESULTS: FMD of the brachial artery in CAL group (5.2% +/- 1.9%) and normal coronary arteries group (6.8% +/- 2.0%) were significantly lower than that of control group (13.2% +/- 4.1%, both P < 0. 01); carotid artery stiffness index in CAL group (4.0 +/- 0.6) was significantly greater than that of normal coronary arteries group (3.6 +/- 0.6) and control group (3.4 +/- 0.5, P = 0.05, P < 0.01); likewise, IMT in CAL group (0.447 mm +/- 0.024 mm) was significantly higher than that of normal coronary arteries group (0.426 mm +/- 0.016 mm) and control group (0.424 mm +/- 0.016 mm, both P < 0.01). In multiple linear regression analysis, age and patient grouping were significant determinants of carotid artery stiffness index, FMD and IMT. There were significant correlations between carotid artery stiffness index, FMD and IMT in both healthy group and KD group after adjustment of age. CONCLUSION: There were endothelial dysfunction and increased systemic arterial stiffness and IMT late after the acute phase of Kawasaki disease. flow-mediated dilation of the brachial artery, carotid artery stiffness index combined carotid intima-media thickness can evaluated completely the prognosis of vascular lesion in convalescence after KD.

Methodological study on real-time three-dimensional echo-cardiography and its application in the diagnosis of complex congenital heart disease.

BACKGROUND: Real-time three-dimensional echocardiography (RT-3DE) has made revolutionized improvements of cardiac imaging during the past few years. However, there is no standard examination method for RT-3DE so far. This study aimed to establish the diagnostic method of RT-3DE and evaluate its application in the diagnosis of complex congenital heart diseases (CHD). METHODS: Fifty patients with complex CHD were examined by RT-3DE with modes of Live 3DE and Full Volume. A series of novel volumetric views combined with Van Praagh sequential segmental approach were introduced to reveal the pathological morphology of the hearts, which were compared with the findings of two-dimensional echocardiography (2DE), angiography and cardiac surgery. RESULTS: In 50 patients, 190 image acquisitions of Full Volume were performed at several acoustic windows including subcostal, apical and parasternal regions. Among them, 94.2% (179/190) of image acquisitions were successful. Most sectional volumetric views could be clearly displayed in 92.6% of the successful image acquisitions. However, sectional volumetric views could not be clearly displayed in 7.4%, which was mainly due to poor perspective conditions of examination location, improper instrument multi-parameter setting and insufficient information of whole heart captured in Full Volume acquisitions. As compared with surgical findings and angiography, RT-3DE made correction to the diagnoses in 2 cases including 1 with corrected transposition of the great arteries and the other with single atrium and mitral cleft. The diagnoses initially made by 2DE for these 2 patients were double outlet right ventricle with transposition of the great arteries and complete atrio-ventricular septal defect. CONCLUSIONS: RT-3DE can clearly display the pathological morphology of complex CHD by a series of novel volumetric views combined with sequential segmental approach through providing more spatial informative cardiovascular structures, which provides a practical method for RT-3DE diagnosis.