By the charge integration method, the dependence of polarization on temperature
is measured for TGS, ATGS, and DTGS ferroelectric crystals, when these crystals are
cooled from the paraelectric phase to room temperature under the condition of short or
open circuit. The experimental results show that the depolarization field produced
during cooling under open circuit strongly influences the reconstruction of domain,
and that the reversion of domain can be caused during heating under short circuit. TGS
crystal can be made monodomain in part and DTGS crystal can be protected from
depolarization when these crystals are cooled under short circuit. The tendency of
spontaneous monodomain in DTGS is explained by using a model of unequal depth-
double well potential.
Ca Cu 3 Ti 4 O 12 (CCTO) ceramics are prepared by the conventional solid-state reaction method under various sintering temperatures from 1000to1120°C at an interval of 10°C. Microstructures and crystalline structures are examined by scanning electronic microscopy and x-ray diffraction, respectively. Dielectric properties and complex impedances are investigated within the frequency range of 40Hz–110MHz over the temperature region from room temperature to 350°C. It has been disclosed that the microstructures can be categorized into three different types: type A (with the small but uniform grain sizes), type B (with the bimodal distribution of grain sizes) and type C (with the large and uniform grain sizes), respectively. The largeness of low-frequency dielectric permittivity at room temperature is closely related to the microstructure. Ceramics with different types of microstructures show the diverse temperature-dependent behaviors of electrical properties. However, the existence of some common characteristics is also found among them. For all of the ceramics, a Debye-type relaxation emerges in the frequency range of 100Hz–100kHz at high measuring temperatures, which has the larger dielectric dispersion strength than the one known in the frequency range above 100kHz. Thus, the high-temperature dielectric dispersion exhibits a large low-frequency response and two Debye-type relaxations. Furthermore, all of the ceramics show three semicircles in the complex impedance plane. These semicircles are considered to represent individually different electrical mechanisms, among which the one in the low-frequency range arises most probably from the contribution of the domain boundaries, and the other two are ascribed to the contributions of the domains and the grain boundaries, respectively.
Atherosclerosis is a very complex process influenced by various systemic and local factors. Therefore, in patients with bilateral carotid plaques (BCPs), there may be differences in carotid plaque vulnerability between the sides. We aimed to investigate the differences in BCP characteristics in patients with BCPs using magnetic resonance vessel wall imaging (MR-VWI).Participants with BCPs were selected for subanalysis from a multicentre study of Chinese Atherosclerosis Risk Evaluation II. We measured carotid plaque burden, identified each plaque component and measured their volume or area bilaterally on MR-VWI. Paired comparisons of the burden and components of BCPs were performed.In all, 540 patients with BCPs were eligible for analysis. Compared with the right carotid artery (CA), larger mean lumen area (p<0.001), larger mean wall area (p=0.025), larger mean total vessel area (p<0.001) and smaller normalised wall index (p=0.006) were found in the left CA. Regarding plaque components, only the prevalence of lipid-rich necrotic core (LRNC) in the left CA was higher (p=0.026). For patients with a vulnerable plaque component coexisting on both sides, only the intraplaque haemorrhage (IPH) volume (p=0.011) was significantly greater in the left CA than in the right CA.There were asymmetries in plaque growth and evolution between BCPs. The left carotid plaques were more likely to have larger plaque burden, higher prevalence of LRNC and greater IPH volume, which may contribute to the lateralisation of ischaemic stroke in the cerebral hemispheres.
To determine the bilaterally asymmetrical associations between extracranial carotid artery atherosclerosis and ipsilateral middle cerebral artery (MCA) stenosis in symptomatic patients using magnetic resonance vessel wall imaging. Approach and Results: Patients with symptomatic carotid artery atherosclerosis were recruited from the Chinese Atherosclerosis Risk Evaluation, a multicenter study. All subjects underwent intracranial magnetic resonance angiography and extracranial carotid artery magnetic resonance imaging. Severe stenosis (stenosis ≥50%) of MCA, carotid moderate-to-severe stenosis (stenosis ≥50%), plaque compositions, and high-risk plaque on symptomatic side were evaluated in all subjects. Associations between ipsilateral MCA stenosis and extracranial carotid plaque features were evaluated. A total of 363 patients (mean age: 61.2±10.4 years old; 254 males) were included. In the left symptomatic cerebrovascular group (n=186), carotid moderate-to-severe stenosis (odds ratio [OR], 3.00 [95% CI, 1.03-8.79]; P=0.045), intraplaque hemorrhage (OR, 3.68 [95% CI, 1.21-11.19]; P=0.021), fibrous cap rupture (OR, 5.70 [95% CI, 1.60-20.31]; P=0.007), and high-risk plaque (OR, 2.95 [95% CI, 1.19-7.35]; P=0.020) were significantly associated with ipsilateral severe MCA stenosis, after adjusting for confounding factors. In the right symptomatic cerebrovascular group (n=177), severe MCA stenosis was significantly associated with ipsilateral carotid moderate-to-severe stenosis (OR, 3.98 [95% CI, 1.54-10.32]; P=0.004) but not with other extracranial carotid plaque features (all P>0.05), after adjusting for confounding factors.In the symptomatic arteries, vulnerable plaque features are independently associated with ipsilateral severe MCA stenosis on the left side, but this association is not found on the right side, indicating the associations of atherosclerotic disease between intracranial and extracranial carotid arteries are asymmetrical.
The epipteric bones of 1262 Chinese adult crania (892 males and 370 females) wereinvestigated. Their forms are divided into three main classes according to their positions,numbers and articulations with pteric bones: namely, single os epiptericum, double, andmultiple ossa epipterica. In 2220 sides of skulls observed the percentage of the single osepiptericum is much higher (18.78%) than that of the other two classes (6.98% and 5.45%).The percentage of epipterics found in all cases is 31.22%. The differences between thetwo sides are almost negligible, while their sexual differences are quite significant, the femalevalue being appreciably higher. Forms of the single os epiptericum include twelve different types. Among them, osepiptericum posterius was found in 180 cases or 8.11%; os epiptericum typicum in 117cases or 5.27%; and os epiptericum anterius in 64 cases or 2.88%. Percentages of othernine types were all less than 0.7%. Forms of the double ossa epipterica can be classified under two types, i.e. the unitedand the separated. The first type occurs in 99 cases or 4.46% and that of the second in56 cases or 2.52%. Forms of the multiple ossa epipterica consist of three types, i.e. the united, the separated,and the combined. Percentages of the three types are 2.97%, 2.12% and 0.36% respectively. Of 1262 crania examined, the epipterics that occurred on both sides were found in144 cases or 11.49%, and those that occurred on one side with the pterion on the otherside found in 301 cases or 23.95%. In the latter the percentage of the spheno-parietalpterion (H type) that paired with the epipteric bone, is extraordinarily high (95.02%).
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