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In this study, stereo particle imaging velocimetry measurements are performed at multiple streamwise locations behind a yawed wind turbine to reveal the formation mechanisms of the counter-rotating vortex pair (CVP), and a point vortex transportation (PVT) model is proposed to reproduce the top–down asymmetric kidney-shaped wake (also referred to as a curled wake). Results indicate that the CVP formed behind a yawed wind turbine originates from the complex interactions between the hub vortex and the streamwise components of the blade tip vortices, which is fundamentally different from the case of a yawed drag disk where the hub vortex is absent. Specifically, when the yaw angle exceeds a critical value, a small part of the streamwise vorticity shed from the rotor disk edge switches its sign from negative to positive and subsequently merges with the concentrated hub vortex under mutual induction, creating a patch of positive vorticity; meanwhile, the remaining streamwise vorticity distributed along the rotor edge curls and evolves into another patch of negative vorticity. These two patches of streamwise vorticity essentially constitute the CVP. Based on the physics learnt from the experiments, the non-uniform cross-stream velocity fields are first reconstructed by a cloud of point vortices distributed along the rotor edge and a hub vortex located in the rotor centre, and subsequently used to numerically solve a simplified transportation–diffusion equation of the wake velocity deficit, which altogether constitute the PVT model. This physics-based reduced-order model is the first model capable of accurately reproducing the wake deformation behind a yawed wind turbine.
Analytical wind turbine wake models and wake superposition methods are prevailing tools widely adopted by the wind energy community to predict the power production of wind farms. However, none of the existing wake superposition methods conserve the streamwise momentum. In this study, a novel wake superposition method capable of conserving the total momentum deficit in the streamwise direction is derived theoretically, and its performance is validated with both particle imaging velocimetry measurements and large-eddy simulation results. Detailed inter-method comparisons show that the novel wake superposition method outperforms all the existing methods by delivering an accurate prediction of the power production and the centreline wake velocity deficit, with a typical error of less than 5 % (excluding the near-wake region). Additionally, the momentum-conserving wake superposition method is extended to combine the transverse velocities induced by yawed wind turbines, and the secondary wake steering effect crucial to the power optimization in active wake control is well reproduced.
The Xiong’ershan area is the third largest gold-producing district in China. The Late Jurassic to Early Cretaceous magmatism in the Xiong’ershan area can be divided into two episodes: early (165–150 Ma) and late (138–113 Ma). Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) zircon U–Pb dating yields ages of 160.7 ± 0.6 Ma and 127.2 ± 1.0 Ma for the Wuzhangshan and Huashan monzogranites in the Xiong’ershan area, respectively, representing the two magmatic episodes. The Wuzhangshan monzogranites exhibit adakite-like geochemical features (e.g. high Sr/Y ratios, low Yb and Y contents). Their Sr–Nd–Hf isotopic compositions are consistent with those of the amphibolites of the Taihua Group, indicating that the Wuzhangshan monzogranites were formed from partial melting of the Taihua Group metamorphic rocks. Compared to the Wuzhangshan rocks, the Huashan monzogranites have higher MgO, Cr, Co and Ni contents, but lower Sr/Y and Fe3+/Fe2+. All the samples from the Huashan monzogranites plot in the area between the Taihua Group amphibolite rocks and the mantle rocks in the (87Sr/86Sr)t vs εNd(t) and age vs εHf(t) diagrams, suggesting that the Huashan monzogranites were probably generated by mixing of mantle-derived magmas and the Taihua Group metamorphic basement melts. The gold mineralization (136–110 Ma) is coeval with the emplacement of the late-episode magmas, implying that crustal–mantle mixed magma might be a better target for gold mineralization compared to the ancient metamorphic basement melt. The data presented in this study further indicate that the transformation of the lithosphere from thickening to thinning in the Xiong’ershan area probably occurred between ~160 Ma and ~127 Ma, and that the gold mineralization in this area was probably related to lithospheric thinning.
The widespread, rapid evolution of herbicide-resistant weeds is a serious and escalating agronomic problem worldwide. During China’s economic boom, the country became one of the most important herbicide producers and consumers in the world, and herbicide resistance has dramatically increased in the past decade and has become a serious threat to agriculture. Here, following an evidence-based PRISMA (preferred reporting items for systematic reviews and meta-analyses) approach, we carried out a systematic review to quantitatively assess herbicide resistance in China. Multiple weed species, including 26, 18, 11, 9, 5, 5, 4, and 3 species in rice (Oryza sativa L.), wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.], corn (Zea mays L.), canola (Brassica napus L.), cotton (Gossypium hirsutum L.)., orchards, and peanut (Arachis hypogaea L.) fields, respectively, have developed herbicide resistance. Acetolactate synthase inhibitors, acetyl-CoA carboxylase inhibitors, and synthetic auxin herbicides are the most resistance-prone herbicides and are the most frequently used mechanisms of action, followed by 5-enolpyruvylshikimate-3-phosphate synthase inhibitors and protoporphyrinogen oxidase inhibitors. The lack of alternative herbicides to manage weeds that exhibit cross-resistance or multiple resistance (or both) is an emerging issue and poses one of the greatest threats challenging the crop production and food safety both in China and globally.
The aim of the present study is to use the syndemic framework to investigate the risk of contracting HIV in the US population. Cross-sectional analyses are from The National Health and Nutrition Examination Survey. We extracted and aggregated data on HIV antibody test, socio-demographic characteristics, alcohol use, drug use, depression, sexual behaviours and sexually transmitted diseases from cycle 2009–2010 to 2015–2016. We carried out weighted regression among young adults (20–39 years) and adults (40–59 years) separately. In total, 5230 men and 5794 women aged 20–59 years were included in the present analyses. In total, 0.8% men and 0.2% women were tested HIV-positive. Each increasing HIV risk behaviour was associated with elevated odds of being tested HIV-positive (1.15, 95% CI 1.15–1.15) among young adults and adults (1.61, 95% CI 1.61–1.61). Multi-faceted, community-based interventions are urgently required to reduce the incidence of HIV in the USA.
The performance of immune system is vital for defending the body from pathogens, and it plays a crucial role in health homoeostasis. In a previous study, we have shown that LFP-20, a twenty-amino acid antimicrobial peptide in the N terminus of porcine lactoferrin, modulated inflammatory response in colitis. Here, we further investigated the effects of LFP-20 on immune homoeostasis to elucidate the mechanism of its anti-inflammation action. A lipopolysaccharide (LPS)-triggered systemic inflammatory response mice model was established. On the basis of observed mucosal lesions and apoptosis in small intestine, we found increased macrophage and neutrophil infiltration in ileum after LPS stimulation. Expectedly, LFP-20 pre-treatment attenuated the LPS-mediated immune disorders in ileum. Moreover, the flow cytometry results indicated pre-treatment with LFP-20 sustained the balance of CD3+CD8+ T cells, B cells and natural killer cells in LPS-triggered immune disturbance. Simultaneously, we demonstrated LFP-20 modulated the secretion of both activated Th1-related IL-12p70, interferon-γ, TNF-α and Th2-related IL-4, IL-5 and IL-6. Furthermore, we found LFP-20 facilitated a balanced Th1 and Th2 response, which triggered cellular defence mechanisms and induced B cells to produce opsonising antibodies belonging to certain IgG subclasses to defend against LPS stimulation. Collectively, our study indicated pre-treatment with LFP-20 could defend against LPS-triggered systemic inflammatory response in mice via modulating immune homoeostasis.
Plasma synthetic jet actuators (PSJAs) are particularly suited for high-Reynolds-number, high-speed flow control due to their unique capability of generating supersonic pulsed jets at high frequency (
kHz). Different from conventional synthetic jets driven by oscillating piezoelectric diaphragms, the exit-velocity variation of plasma synthetic jets (PSJs) within one period is significantly asymmetric, with ingestion being relatively weaker (less than
) and longer than ejection. In this study, high-speed phase-locked particle image velocimetry is employed to investigate the interaction between PSJAs (round exit orifice, diameter 2 mm) and a turbulent boundary layer at constant Strouhal number (0.02) and increasing mean velocity ratio (
, defined as the ratio of the time-mean velocity over the ejection phase to the free-stream velocity). Two distinct operational regimes are identified for all the tested cases, separated by a transition velocity ratio, lying between
. At large velocity and stroke ratios (first regime, representative case
), vortex rings are followed by a trailing jet column and tilt downstream initially. This downstream tilting is transformed into upstream tilting after the pinch-off of the trailing jet column. The moment of this transformation relative to the discharge advances with decreasing velocity ratio. Shear-layer vortices (SVs) and a hanging vortex pair (HVP) are identified in the windward and leeward sides of the jet body, respectively. The HVP is initially erect and evolves into an inclined primary counter-rotating vortex pair (
-CVP) which branches from the middle of the front vortex ring and extends to the near-wall region. The two legs of the
-CVP are bridged by SVs, and a secondary counter-rotating vortex pair (
-CVP) is induced underneath these two legs. At low velocity and stroke ratios (second regime, representative case
), the trailing jet column and
-CVP are absent. Vortex rings always tilt upstream, and the pitching angle increases monotonically with time. An
-CVP in the near-wall region is induced directly by the two longitudinal edges of the ring. Inspection of spanwise planes (
-plane) reveals that boundary-layer energization is realized by the downwash effect of either vortex rings or
-CVP. In addition, in the streamwise symmetry plane, the increasing wall shear stress is attributed to the removal of low-energy flow by ingestion. The downwash effect of the
-CVP does not benefit boundary-layer energization, as the flow swept to the wall is of low energy.
Little is known of the olfactory mechanisms of host detection in the ovipositors of endoparasitoids and ectoparasitoids. An endoparasitoid Aprostocetus causalis La Salle & Wu (Hymenoptera: Eulophidae) and an ectoparasitoid Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae: Tetrastichinae) are the two parasitoids of the eucalyptus gall wasp Leptocybe spp. Structures and sense organs of ovipositors of A. causalis and Q. mendeli were studied using scanning and transmission electron microscopy, which provided essential information for exploring the mechanism of host detection by endoparasitoid and ectoparasitoid. The ovipositors of two parasitoids consisted of the first and second valvulae and ended in a pointed tip. There were three types of microtrichia, two types of sensilla chaetica, and one type of sensilla campaniformia on the ovipositors of A. causalis and Q. mendeli. However, Q. mendeli has the fourth type of microtrichia on the ovipositor. The morphology, types, distribution, length, and width of these sensilla and microtrichia were described, and their possible functions are discussed in conjunction with the stinging, oviposition, and the host selection process.
The consumption of nitrate-rich vegetables can acutely lower blood pressure and improve mediators shown to optimise vascular health. However, we do not yet understand the impact of long-term habitual dietary nitrate intake and its association with CVD. Therefore, the aim of this investigation was to examine the relationship between habitual dietary nitrate intakes and risk of CHD in women from the Nurses’ Health Study. We prospectively followed 62 535 women who were free from diabetes, CVD and cancer at baseline in 1986. Information on diet was updated every 4 years with validated FFQ. The main outcome was CHD defined by the occurrence of non-fatal myocardial infarction or fatal CHD. Cox proportional hazard regression models were used to estimate the relative risks (RR) and 95 % CI. During 26 years of follow-up, 2257 cases of CHD were identified. When comparing the highest quintile of nitrate intake with the lowest quintile, in aged-adjusted analysis there was a protective association for CHD (RR=0·77, 95 % CI 0·68, 0·97; P=0·0002) which dissipated after further adjustment for smoking, physical activity, BMI and race (RR=0·91; 95 % CI 0·80, 1·04; P=0·27). This magnitude of association was further attenuated once we adjusted for the Alternative Healthy Eating Index excluding vegetable and fruit consumption (RR=1·04, 95 % CI 0·91, 1·20; P=0·34). Dietary nitrate intake was not related to the risk of CHD after adjustment for other lifestyle and non-vegetable dietary factors in a large group of US women.
Pumped by rectangular-shaped dissipative soliton resonance (DSR) pulses at 1030 nm, selective excitations of Raman Stokes lines of up to third order with extinction ratios of 8 dB and fifth order with extinction ratios of 4 dB are demonstrated experimentally. The rectangular DSR pulses are generated from a dual-amplifier ytterbium-doped figure-of-eight mode-locked laser constructed using all
-core-diameter large-mode-area fibers. By varying the two pump powers, the peak power of the output DSR pulses can be continuously tuned from 10 W to 100 W and from 30 W to 200 W, respectively, for two different lengths of the nonlinear amplifying loop mirror inside the cavity. High-frequency components are found to correspond to parts of the pulse in the trailing edge when two bandpass filters are used to separate the propagated pulse. Consequently, it provides an all-fiber technique to achieve selective excitation of the Raman shift by adjusting the peak power of the DSR pulse.
Living Caprini are dominant bovids in the pan-Tibetan area that are strongly adapted to dry steppe and high-mountain meadow habitats. Some taxa with Holarctic distributions, e.g., Ovis Linnaeus, 1758, were thought to originate on the Tibetan Plateau and subsequently dispersed elsewhere, which was depicted as an ‘out of Tibet’ story. However, except for some information on a stem caprine assemblage from the Qaidam Basin, the early evolution of Caprini around the Tibetan Plateau is poorly known. Here, we report new material of Olonbulukia tsaidamensis Bohlin, 1937, which was a member of this stem caprine assemblage, from the Wuzhong region, northern China, confirming the similarity of the Wuzhong Fauna and ‘Qaidam Fauna.’ Based on a biometric study of horncores from the ‘Qaidam’ and Wuzhong faunas, we recognize six taxa from this stem caprine assemblage: O. tsaidamensis, O. sp., Qurliqnoria cheni Bohlin, 1937, Tossunnoria pseudibex Bohlin, 1937, ?Protoryx cf. P. enanus Köhler, 1987, and cf. Pachytragus sp. Among these taxa, Q. cheni and T. pseudibex are probably related to some extant Tibetan endemic species, e.g., the Tibetan antelope, Pantholops hodgsonii (Abel, 1826), and the Himalayan tahr, Hemitragus jemlahicus (Smith, 1826). Others might be ancestral to the Turolian caprine assemblages and even possibly gave rise to the extant Caprina. This work reveals an early radiation of stem caprines along the northern side of the rising Tibetan Plateau and indicates a mixed pattern of pan-Tibetan stem caprine evolution prior to their dispersal out of the Tibetan Plateau.
In 1885, Fedorov discovered that a convex domain can form a lattice tiling of the Euclidean plane if and only if it is a parallelogram or a centrally symmetric hexagon. This paper proves the following results. Except for parallelograms and centrally symmetric hexagons, there are no other convex domains that can form two-, three- or four-fold lattice tilings in the Euclidean plane. However, there are both octagons and decagons that can form five-fold lattice tilings. Whenever
, there are non-parallelohedral polytopes that can form five-fold lattice tilings in the
-dimensional Euclidean space.
Inappropriate use of antibiotics is contributing to a serious antimicrobial resistance problem in Asian hospitals. Despite resource constraints in the region, all Asian hospitals should implement antimicrobial stewardship (AMS) programs to optimize antibiotic treatment, improve patient outcomes, and minimize antimicrobial resistance. This document describes a consensus statement from a panel of regional experts to help multidisciplinary AMS teams design programs that suit the needs and resources of their hospitals. In general, AMS teams must decide on appropriate interventions (eg, prospective audit and/or formulary restriction) for their hospital, focusing on the most misused antibiotics and problematic multidrug-resistant organisms. This focus is likely to include carbapenem use with the goal to reduce carbapenem-resistant gram-negative bacteria. Rather than initially trying to introduce a comprehensive, hospital-wide AMS program, it would be practical to begin by pilot testing a simple program based on 1 achievable core intervention for the hospital. AMS team members must work together to determine the most suitable AMS interventions to implement in their hospitals and how best to put them into practice. Continuous monitoring and feedback of outcomes to the AMS teams, hospital administration, and prescribers will enhance sustainability of the AMS programs.
High-energy electron radiography (HEER) has been proposed for time-resolved imaging of materials, high-energy density matter, and for inertial confinement fusion. The areal-density resolution, determined by the image intensity information is critical for these types of diagnostics. Preliminary experimental studies for different materials with the same thickness and the same areal-density target have been imaged and analyzed. Although there are some discrepancies between experimental and theory analysis, the results show that the density distribution can indeed be attained from HEER. The reason for the discrepancies has been investigated and indicates the importance of the uniformity in the transverse distribution beam illuminating the target. Furthermore, the method for generating a uniform transverse distribution beam using octupole magnets was studied and verified by simulations. The simulations also confirm that the octupole field does not affect the angle-position correlation in the center part beam, a critical requirement for the imaging lens. A more practical method for HEER using collimators and octupoles for generating more uniform beams is also described. Detailed experimental results and simulation studies are presented in this paper.
The antennal sensilla of female Quadrastichus mendeli Kim & La Salle (Hymenoptera: Eulophidae: Tetrastichinae) were observed with scanning and transmission electron microscopy in this study. The antenna of Q. mendeli was geniculate, and the flagellum was composed of seven subsegments. Six distinct types of sensory receptors were observed, including sensilla basiconic capitate peg, sensilla böhm, sensilla chaetica, sensilla campaniformia, sensilla placodea and sensilla trichodea. Sensilla basiconic capitate pegs were found on the flagellomeres, and Böhm sensilla were found on the basal part of scape and the pedicel. Two morphological subtypes of sensilla chaetica were found on the antennae, and sensilla campaniformia were only found on the pedicel. Sensilla placodea were divided into two morphological subtypes that were found on the flagellomeres. Sensilla trichodea were found on the 2nd–6th flagellomere. By comparison to existing antennal sensilla, it was found that sensilla basiconic capitate peg, sensilla chaetica, sensilla placodea and sensilla trichodea were the most common sensilla of the parasitoids of Eulophidae. The external and internal morphology, types, number, distribution, length, and width of these sensilla were described, and their possible functions are discussed in conjunction with the host-detection behavior. Future studies on the host location mechanisms in Q. mendeli will be facilitated by these observations.
Environmental characteristics (for example, temperature, photoperiod) as seasonal cues can affect the offspring sex ratio and reproductive tactics of many hymenopteran insects. Leptocybe invasa Fisher & La Salle is the most critical invasive insect pest of Eucalyptus spp. in the world and displays thelytokous reproduction. In the current study, we studied the effects of temperature and photoperiod on offspring sex ratio and reproductive tactics in L. invasa. Results show that sex ratio (female: male) of L. invasa was under 15, 25 and 35 °C with both L 12: D 12 and L 16: D 8, and cold and thermal acclimation were 74.5:1, 71.0:1, 59.0:0, 17.3:1, 53.0:0, 64.0:0, 47.0:1 and 56.0:0, respectively, which was highly significantly female biased and with no significant difference due to temperature or photoperiod. Offspring virgin females oviposited and induced the bump-shaped galls on plants under the same conditions as described above. Constant temperature, photoperiod and their interaction, and cold and thermal acclimation had no significant effect on the infestation rates of Eucalyptus branches induced by offspring virgin females. Thus, temperature, photoperiod and cold and thermal acclimation did not influence female-biased sex ratio and tactics with thelytokous reproduction of offspring females in L. invasa.
In this study, a facile room-temperature solution method is developed for the preparation of zinc oxide@graphene oxide (ZnO@GO) nanocomposites. Unlike the general process to obtain crystallized materials by heating, the room temperature we used can generate fine ZnO@GO nanocomposites with ultra-small ZnO nanocrystal (∼8 nm) and high weight content (∼84%). The obtained ZnO@GO nanocomposite was thoroughly characterized by various physicochemical techniques such as scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy, indicating well-dispersed ZnO on the GO layer and strong interaction between the each other. As an anode material for lithium-ion batteries, ZnO@GO exhibits high specific reversible capacity and excellent cycling performance, which can be ascribed to the role of GO in preventing the agglomeration of the ZnO nanoparticles by creating the decorated nanoscale composite during the electrochemical process.
Stability of a plasma cylinder with a current wrapped by a helical plasma flow is studied. Unstable surface modes of magnetohydrodynamic (MHD) oscillations develop at the boundary of the cylinder enwrapped by the plasma flow. Unstable eigenmodes can also develop for which the plasma cylinder is a waveguide. The growth rate of the surface modes is much higher than that for the eigenmodes. It is shown that the asymmetric MHD modes in the plasma cylinder are stable if the velocity of the plasma flow is below a certain threshold. Such a plasma flow velocity threshold is absent for the symmetric modes. They are unstable in any arbitrarily slow plasma flows. For all surface modes there is an upper threshold for the flow velocity above which they are stable. The helicity index of the flow around the plasma cylinder significantly affects both the Mach number dependence of the surface wave growth rate and the velocity threshold values. The higher the index, the lower the upper threshold of the velocity jump above which the surface waves become stable. Calculations have been carried out for the growth rates of unstable oscillations in an equilibrium plasma cylinder with current serving as a model of the low-latitude boundary layer (LLBL) of the Earth’s magnetic tail. A tangential discontinuity model is used to simulate the geomagnetic tail boundary. It is shown that the magnetopause in the geotail LLBL is unstable to a surface wave (having the highest growth rate) in low- and medium-speed solar wind flows, but becomes stable to this wave in high-speed flows. However, it can remain weakly unstable to the radiative modes of MHD oscillations.
Plasma synthetic jet actuators (PSJAs), capable of producing high-velocity pulsed jets at high frequency, are well suited for high-Reynolds-number subsonic and supersonic flow control. The effects of energy deposition and actuation frequency on the formation and evolution characteristics of plasma synthetic jets (PSJs) are investigated in detail by high-speed phase-locked particle imaging velocimetry (PIV). Increasing jet intensity with energy deposition is mainly contributed by the increasing peak jet velocity (
), while decreasing jet intensity with actuation frequency is attributed to both the reduced cavity density (primary factor) and the shortened jet duration (secondary factor). The total energy efficiency of the considered PSJA (
) reduces monotonically with increasing frequency, while the time-averaged thrust produced by the PSJA is positively proportional to both the deposition energy and the frequency. A simplified theoretical model is derived and reveals a scaling power law between the peak jet velocity and the non-dimensional deposition energy (exponent
). The propagation velocity of the vortex ring attached at the jet front shows a non-monotonic behaviour of initial sharp increase and subsequent mild decay. The peak values for both the propagation velocity and the circulation of the front vortex ring are reached approximately two exit diameters away from the exit. Finally, analysis of the time-averaged flow fields of the issuing PSJ indicates that the axial decay rate of the centreline velocity is proportional to the actuation frequency whereas it is invariant with the energy deposition. The jet spreading rate of the PSJ is found to be higher than steady jets but lower than piezoelectric synthetic jets. Similarly, the entrainment coefficients of the PSJ are found to be twice as high as the values for comparable steady jets.