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A dual-band angular-stable transmissive linear to circular polarization converter based on metasurface is proposed and demonstrated in this work. The converter consists of three layers. The top and bottom layers are formed by an array of double split-ring layers. The unit cell of the central layer contains a square loop nesting a slant dipole. The split-rings create two resonances, enabling dual-band operation. The slant dipole and square loop are useful for improving the quality of circular polarization conversion. It is shown that the proposed polarization converter converts the incident linearly polarized wave into circularly polarized wave with opposite polarization modes over the frequency ranges of 8.77–10.58 and 17.59–19.88 GHz. The angular stability is up to 60° for 3 dB axial ratio. Moreover, the thickness of unit cell has a wavelength below 0.06 at the lower band. Compared with other designs in the literature, the structure bears merits of wideband response, high angular stability, and low-profile property within dual-band operational region. To validate the design, a sample prototype was designed, fabricated, and measured. The measured results are in good agreement with the simulated ones.
Vascular dementia (VD) is one of the more common types of dementia. Much is known about VD in older adults in terms of survival and associated risk factors, but comparatively less is known about VD in a younger population. This study aimed to investigate survival in people with young-onset VD (YO-VD) compared to those with late-onset VD (LO-VD) and to investigate predictors of mortality.
Retrospective file review from 1992 to 2014.
The inpatient unit of a tertiary neuropsychiatry service in Victoria, Australia.
Inpatients with a diagnosis of VD.
Measurements and methods:
Mortality information was obtained from the Australian Institute of Health and Welfare. Clinical variables included age of onset, sex, vascular risk factors, structural neuroimaging, and Hachinksi scores. Statistical analyses used were Kaplan–Meier curves for median survival and Cox regression for predictors of mortality.
Eighty-four participants were included with few clinical differences between the LO-VD and YO-VD groups. Sixty-eight (81%) had died. Median survival was 9.9 years (95% confidence interval 7.9, 11.7), with those with LO-VD having significantly shorter survival compared to those with YO-VD (6.1 years and 12.8 years, respectively) and proportionally more with LO-VD had died (94.6%) compared to those with YO-VD (67.5%), χ2(1) = 9.16, p = 0.002. The only significant predictor of mortality was increasing age (p = 0.001).
While there were few clinical differences, and older age was the only factor associated with survival, further research into the effects of managing cardiovascular risk factors and their impact on survival are recommended.
To investigate whether genetic variants in methylenetetrahydrofolate reductase (MTHFR) and methylenetetrahydrofolate dehydrogenase (MTHFD) genes are associated with risk of congenital cardiac disease.
Accumulative evidence suggests that hyperhomocysteinaemia is associated with risk of congenital cardiac disease. Inherited polymorphisms in key folate metabolic pathway genes, MTHFR and MTHFD, may influence the efficiency of folate metabolism and plasma level of homocysteine.
A two-stage case–control study of congenital cardiac disease was conducted by genotyping MTHFR c.1793G>A and four other variants – MTHFR c.677C>T, c.1298A>C, and MTHFD c.1958G>A, c.401C>T – in a Chinese population consisting of 1033 congenital cardiac disease patients and 1067 non-congenital cardiac disease patients.
The variant genotypes of MTHFR c.1793GA/AA were associated with a significantly decreased risk of congenital cardiac disease in two stages combined, with an adjusted odds ratio of 0.67 and a 95% confidence interval of 0.54–0.84 (p = 0.0004). In comparison with wild-type homozygote c.1793GG, the effect was significant in isolated perimembranous ventricular septal defect patients with an adjusted odds ratio of 0.60 and a 95% confidence interval of 0.43–0.83 (p = 0.0003).
These findings indicate that MTHFR c.1793G>A may have a role in susceptibility to sporadic congenital cardiac disease.
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