RESUMO
The magneto-electro-elastic (MEE) medium is a typical intelligent material with promising application prospects in sensors and transducers, whose thermal contact response is responsible for their sensitivity and stability. An effective thermal contact model between a moving sphere and a coated MEE medium with transverse isotropy is established via a semi-analytical method (SAM) to explore its thermal contact response. First, a group of frequency response functions for the magneto-electro-thermo-elastic field of a coated medium are derived, assuming that the coating is perfectly bonded to the substrate. Then, with the aid of the discrete convolution-fast Fourier transform algorithm and conjugate gradient method, the contact pressure and heat flux can be determined. Subsequently, the induced elastic, thermal, electric and magnetic fields in the coating and substrate can be obtained via influence coefficients relating the induced field and external loads. With the proposed method, parametric studies on the influence of the sliding velocity and coating property are conducted to investigate the thermal contact behavior and resulting field responses of the MEE material. The sliding velocity and thermal properties of the coating have a significant effect on the thermal contact response of the MEE material; the coupled multi-field response can be controlled by changing the coating thickness between ~0.1 a0 and a0.
RESUMO
OBJECTIVE: To determine the relationship between the serum sulfur dioxide, homocysteine and the pulmonary arterial pressure in children with congenital heart defects who generated a pulmonary arterial hypertension syndrome (PAH-CHD), and analyze their role in the pathological process of the disease. METHOD: This was a prospective cohort study, children with systemic pulmonary shunt CHD were selected. The patients were divided into three groups: the CHD with no PAH group:n = 20, 10 males, 10 females, 5 with ventricular septal defect (VSD), 8 with atrial septal defect (ASD) and 7 with patent ductus arteriosus (PDA), mean age (1.9 ± 1.8) years; the CHD with mild PAH group:n = 20, 10 males, 10 females, 12 with VSD, 6 with ASD, and 2 with PDA, mean age (1.0 ± 0.8) year; the CHD with moderate or severe PAH group:n = 20, 8 males, 12 females, 12 with VSD, 6 with ASD, and 1 with PDA, 1 with ASD+VSD, mean age (1.8 ± 1.6) year. Twenty healthy children were enrolled from outpatient department as the control group [included 8 males, 12 females, mean age (1.9 ± 1.5) years]. The homocysteine and SO2 concentrations in the serum samples were detected by a modified high performance liquid chromatographic method with fluorescence detection (HPLC-FD), then, multiple comparisons among the groups were performed with analysis of variance, and the pearson correlation. RESULT: The serum homocysteine concentrations were respectively (11.0 ± 2.7) , (11.7 ± 2.5), (12.0 ± 2.1), (14.3 ± 3.2) µmol/L in the control group, CHD with no PAH group, CHD with mild PAH group, and CHD with moderate or severe PAH group. According to the multiple comparisons, the CHD with moderate or severe PAH group had the highest level (P all < 0.05) .While the comparison within the control group, CHD with none PAH group, and CHD with mild PAH group, the differences were not significant (P all > 0.05). The serum sulfur dioxide strength (concentrated as SO3(2-)) were respectively (10.6 ± 2.4), (8.9 ± 2.3), (7.3 ± 2.9), (4.3 ± 2.1) µmol/L in the control group, CHD with none PAH group, CHD with mild PAH group, and CHD with moderate or severe PAH group. CHD with moderate or severe PAH group had the highest level of serum sulfur dioxide (P < 0.05) . The pearson correlation analysis indicated that in the CHD children, the serum homocysteine were positively correlated with the pulmonary arterial pressure (r = 0.481, P < 0.01), while, the sulfur dioxide were negatively correlated with pulmonary arterial pressure (r = -0.553, P < 0.01).In all children, the serum homocysteine levels were negatively correlated with the sulfur dioxide (r = -0.231, P = 0.039). CONCLUSION: The PAH-CHD children had higher homocysteine levels and lower sulfur dioxide levelsl, which demonstrated the disturbance of homocysteine-sulfur dioxide pathway in the sulfur containing amino acids metabolish in the disease. The homocysteine may become a biological marker which reflecting the severities of the PAH-CHD, while the sulfur dioxide can be a new target for the therapy of PAH-CHD.
