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This paper investigates a wideband and low axial ratio circularly polarized (CP) antenna, which is composed of a monopole on a novel polarization rotating reflective surface (PRRS) based on a corner-truncated artificial magnetic conductor (AMC) structure. By adjusting the dimensions of truncated corner properly, the PRRS has two polarization rotation (PR) frequency points. Then, a large PR band of 18% (5.55–6.65 GHz) can be achieved with two adjacent PR frequency points coming together. The profile of the newly PRRS is only0.04λ0. With corner-truncated AMC-based PRRS loading, a measured impedance bandwidth of 1.8 GHz (5.4–7.2 GHz) and the 3 dB axial ratio bandwidth of 1 GHz (5.55–6.65 GHz) could be obtained by the monopole antenna and validated by measurements. The values of AR were well below 1 dB at most of the CP region, which show a perfect CP performance. Moreover, the proposed antenna has exhibited a large axial ratio beamwidth in both the xoz- and yoz-planes and a peak gain of 6.1 dBic within the operational bandwidth.
A novel wideband circularly polarized printed antenna is proposed in this paper. It consists of asymmetrical ground and monofilar spiral stubs connecting to it. By employing an inverted L-shaped microstrip feedline to excite the slit etched in the ground and spiral stubs, a wideband culalry polarized performance of the proposed antenna is realized. After optimization, the measured results of the final structure demonstrate that a 10 dB bandwidth of 76.2% from 2.6 to 5.8 GHz and a 3 dB axial-ratio bandwidth for circular polarization of 72.9% from 2.7 to 5.8 GHz could be achieved which could completely cover the Wimax (3.3–3.8 GHz) band.
The construction chronology of three of the earliest Dunhuang Mogao Grottoes (Caves 268, 272, and 275) has been the subject of ongoing debate for over half a century. This chronology is a crucial topic in terms of further understanding of the establishment of the Dunhuang Mogao Grottoes, early Buddhism in the Gansu corridor, and its relationship with Buddhism developed in the Central Plains. Building upon archaeological, art historical and radiocarbon (14C) dating studies, we integrate new 14C data with these previously published findings utilizing Bayesian statistical modeling to improve the chronological resolution of this issue. Thus, we determine that all three of these caves were constructed around AD 410–440, suggesting coeval rather than sequential construction.
A algorithm for digital image centering with the maximum likelihood method is described. The astrometric accuracy of this algorithm is similar to the two-dimensional Gaussian fitting. For saturated images, this algorithm is better than the Gaussian fitting. With the maximum likelihood method, some systematic effect, such as coma and magnitude equation, can be reduced significantly.
The degradation, alteration and depletion of riparian habitats caused by river regulation are among critical conservation concerns. Aquatic and riparian habitats support not only river-dwelling biota such as macroinvertebrates and fish, but also waterbirds, the top predators in the aquatic food web. Despite the intimate relationships between fish and waterbirds, the two groups are often investigated separately. Using an integrative approach, we examined the effects of dams on fish and scaly-sided merganser (Mergus squamatus), an endangered, iconic riverine species, where the lack of knowledge about habitat preferences greatly hampers long-term conservation efforts. Our analysis quantified three causal links: (1) water depth had direct, comparable, negative effects on both fish and waterbirds, and the path coefficients for fish and birds are –0.31 and –0.46, respectively; (2) river landscape heterogeneity directly and positively affected fish and waterbirds, and the path coefficients for fish and birds are 0.63 and 0.19, respectively; and (3) depth and river landscape also exerted indirect effects on waterbirds through their impacts on fish abundance, and the path coefficients for fish and birds are –0.15 and 0.28, respectively. Our findings could contribute to the rational spatial planning and sustainable operation of dams in that maintaining instream habitat availability and heterogeneity would benefit the whole riverine ecosystem.
Massively parallel sequencing (MPS) technology has become increasingly available
and has been widely used to screen for trisomies 21, 18, and 13 in singleton
pregnancies. This study assessed the performance of MPS testing of cell-free
fetal DNA (cffDNA) from maternal plasma for trisomies 21, 18, and 13 in twin
pregnancies. Ninety-two women with twin pregnancies were recruited. The results
were identified through karyotypes of amniocentesis or clinical examination and
follow-up of the neonates. Fluorescent in-situ hybridization was used to examine
the placentas postnatally in cases of false-positive results. The fetuses with
autosomal trisomy 21 (n = 2) and trisomy 15 (n
= 1) were successfully detected via MPS testing of cffDNA. There was one
false-positive for trisomy 13 (n = 1), and fluorescence in-situ
hybridization (FISH) identified confined placental mosaicism in this case. For
twin pregnancies undergoing second-trimester screening for trisomy, MPS testing
of cffDNA is feasible and can enhance the diagnostic spectrum of non-invasive
prenatal testing, which could effectively reduce invasive prenatal diagnostic
methods. In addition to screening for trisomy 21, 18, and 13 by cffDNA, MPS can
detect fetal additional autosomal trisomy. False-positive results cannot
completely exclude confined placental mosaicism.
To reveal the electron and phonon transport mechanism in bismuth nanowire (BiNW), the electronic structure, the lattice dynamics, and the thermoelectric properties of bismuth bulk (BiB) and BiNW were investigated in this paper through first-principles calculation and the Boltzmann transport theory. The results suggest that BiNW possesses an increased electrical conductivity and Seebeck coefficient, while its thermal conductivity, especially phonon thermal conductivity, is reduced significantly as compared to BiB. As a consequence, a largely enhanced figure of merit (ZT) at 300 K of 2.73 is achieved for BiNW. The enhancement in electrical conductivity and Seebeck coefficient of BiNW is originated from its high density of states and large effective mass of carriers. Such significant suppression in phonon thermal conductivity of BiNW is ascribed to the reduced phonon vibration frequency, the decreased phonon density of states, and the shortened mean free path of phonons. So BiNW should be viewed as an excellent candidate for a thermoelectric material with a high figure of merit. Moreover, we have provided a complete understanding on the relationship between the electronic structure, the dynamics, and the thermoelectric properties of BiNW.
To link the optical reference frame to extragalactic radio frame, an observation program is in progress in Purple Mountain Observatory (PMO) and Shanghai Observatory. In this program, 70 extragalactic sources will be observed with the 1.56 m astrometric reflector in Shanghai. The secondary reference stars are determined with the twin astrograph (D = 40 cm, f = 300 cm) in PMO, and about 50 radio stars and some bright extragalactic sources will be observed with the twin astrograph.
Recent studies have suggested an association between vitamin D and non-alcoholic fatty liver disease (NAFLD); however, some results are subject to debate. This study was carried out to evaluate the correlation between NAFLD and vitamin D in men and women in East China. The data were obtained from a cross-sectional study that focused on the health and metabolic status of adults in sixteen areas of East China. According to ultrasonic assessments, the patients were divided into normal and NAFLD groups. Demographic characteristics and biochemical measurements were obtained. Binary logistic regression analysis was used to explore the association. In total, 5066 subjects were enrolled, and 2193 (43·3 %) were diagnosed with NAFLD; 84·56 % of the subjects showed vitamin D deficiency. Subjects with high vitamin D levels had a lower prevalence of NAFLD, particularly male subjects. Within the highest quartile of vitamin D levels, the prevalence of NAFLD was 40·8 %, whereas the lowest quartile of vitamin D levels showed a prevalence of 62·2 %, which was unchanged in women across the vitamin D levels. Binary logistic analysis showed that decreased vitamin D levels were associated with an increased risk of NAFLD (OR 1·54; 95 % CI 1·26, 1·88). This study suggests that vitamin D levels are significantly associated with NAFLD and that vitamin D acts as an independent factor for NAFLD prevalence, particularly in males in East China. Vitamin D interventional treatment might be a new target for controlling NAFLD; elucidating the mechanism requires further research.
Depression is closely associated with quality of life (QOL) in older adults. Being elderly and exhibiting mild depressive symptoms may not lead to a depression diagnosis, but these attributes are clinically important. However, the extent to which these factors influence QOL and its determinants in older adults remains unclear.
Questionnaires were administered to people aged 65 years or older at community senior centers in Taiwan to collect socio-demographic information and to assess results from the brief version of the World Health Organization's Quality of Life instrument (WHOQOL-BREF), Modified Barthel Index (MBI), 15-item Geriatric Depression Scale (GDS), and Mini-Mental State Examination (MMSE). Levels of depressive symptoms were classified as no depressive symptoms (NDS), lower level of depressive symptoms (LLDS), and higher level of depressive symptoms (HLDS), corresponding to GDS = 0, 1≦GDS≦5, and GDS>5, respectively. Multiple linear regression analyses were conducted to assess associations between the WHOQOL-BREF and its covariates for different levels of depressive symptoms.
A total of 454 older adults participated. The GDS and MBI scores significantly affected the WHOQOL-BREF physical and psychological domain scores in the LLDS group. Gender influenced the WHOQOL-BREF scores in the NDS group, and increased age demonstrated protective effects on the three domains in the HLDS group. Moreover, the association between the WHOQOL-BREF and its covariates varied for different levels of depressive symptoms.
Treatment for depressive symptoms is of high priority, and early recognition of and appropriate intervention for mild depressive symptoms may improve community-dwelling older adults’ QOLs.
High-resolution SIMS U–Pb dating of metamorphic zircons of the TTG gneisses, gneissic granitoid and amphibolites of the Lushan terrane, Taihua metamorphic complex, suggests that the metamorphism had taken place at least as early as ~1.96–1.86 Ga. These new dates, along with reference data, demonstrate that the southern and middle terranes of the Trans-North China Orogen had been involved in the continent–continent collision between the Western Block and the Eastern Block of the North China Craton. This orogenic process started as early as 1.96 Ga and lasted as late as 1.80 Ga.
The AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) sample has been grown by MOCVD on (0 0 0 1) sapphire substrate. The structure features a 7 nm In0.046Ga0.954N interlayer determined by Rutherford backscattering (RBS). Since the polarization field in the InGaN interlayer is opposite to it in the AlGaN layer, an additional potential barrier is introduced between the two-dimensional electron gas (2DEG) channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. The GaN layers between the AlGaN layer and InGaN interlayer are divided into two layers consisting of GaN channel layer which provides high mobility 2DEG grown at 1070 °C and GaN spacer layer grown at the same temperature as InGaN interlayer (800 °C) to prevent indium diffusion. RBS measurement confirms that the 3 nm GaN spacer layer isolates the InGaN interlayer well and free from diffusion. Hall measurement has been performed, the mobility as high as 1552 cm2/V s at room temperature is obtained and the sheet carrier density is 1.55 × 1013 cm−2. The average sheet resistance is 331 Ω/sq, respectively. The mobility obtained in this paper is about 20% higher than similar structures reported.