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Glutamine synthetase (GS) and glutamate synthase (GOGAT) play a central role in plant nitrogen (N) metabolism. In order to study the effect of powdery mildew (Blumeria graminis f. sp. tritici, Bgt) on N metabolism, field experiments were carried out to evaluate GS and GOGAT activity, GS expression and grain protein content (GPC) in susceptible (Xi'nong 979) and resistant (Zhengmai 103) wheat cultivars under three treatments. The three treatments were no inoculation (CK), inoculated once with Bgt (MP) and inoculated nine times with Bgt (HP). For Xi'nong 979, the activities of GS and GOGAT in grains as well as GS activity in flag leaves increased at 10–15 days after anthesis (DAA), and decreased significantly at 15 or 20–30 DAA in HP and MP. However, GS activity in grains decreased from 20 DAA, which was later than that of flag leaves (15 DAA). At the same time, GS expression in grains was up-regulated at early stage, with GS1 at 10 DAA and GS2 at 15 DAA, followed by a continuous down-regulation. This result indicated that GS and GOGAT activity as well as GS expression were inhibited by powdery mildew, indicating that N metabolism in grains was inhibited at 20–30 DAA. The current study also found out that the yield of the susceptible cultivar decreased significantly, while its GPC increased obviously in HP. It was shown that the increase of GPC was not due to the enhancement of N metabolism, but due to the passive increase caused by yield reduction.
To investigate the influences of dietary riboflavin (RF) addition on nutrient digestion and rumen fermentation, eight rumen cannulated Holstein bulls were randomly allocated into four treatments in a repeated 4 × 4 Latin square design. Daily addition level of RF for each bull in control, low RF, medium RF and high RF was 0, 300, 600 and 900 mg, respectively. Increasing the addition level of RF, DM intake was not affected, average daily gain tended to be increased linearly and feed conversion ratio decreased linearly. Total tract digestibilities of DM, organic matter, crude protein (CP) and neutral-detergent fibre (NDF) increased linearly. Rumen pH decreased quadratically, and total volatile fatty acids (VFA) increased quadratically. Acetate molar percentage and acetate:propionate ratio increased linearly, but propionate molar percentage and ammonia-N content decreased linearly. Rumen effective degradability of DM increased linearly, NDF increased quadratically but CP was unaltered. Activity of cellulase and populations of total bacteria, protozoa, fungi, dominant cellulolytic bacteria, Prevotella ruminicola and Ruminobacter amylophilus increased linearly. Linear increase was observed for urinary total purine derivatives excretion. The data suggested that dietary RF addition was essential for rumen microbial growth, and no further increase in performance and rumen total VFA concentration was observed when increasing RF level from 600 to 900 mg/d in dairy bulls.
The aim of this study was to explore the frequency and distribution of gene mutations that are related to isoniazid (INH) and rifampin (RIF)-resistance in the strains of the multidrug-resistant tuberculosis (MDR-TB) Mycobacterium tuberculosis (M.tb) in Beijing, China. In this retrospective study, the genotypes of 173 MDR-TB strains were analysed by spoligotyping. The katG, inhA genes and the promoter region of inhA, in which genetic mutations confer INH resistance; and the rpoB gene, in which genetic mutations confer RIF resistance, were sequenced. The percentage of resistance-associated nucleotide alterations among the strains of different genotypes was also analysed. In total, 90.8% (157/173) of the MDR strains belonged to the Beijing genotype. Population characteristics were not significantly different among the strains of different genotypes. In total, 50.3% (87/173) strains had mutations at codon S315T of katG; 16.8% (29/173) of strains had mutations in the inhA promoter region; of them, 5.5% (15/173) had point mutations at −15 base (C→T) of the inhA promoter region. In total, 86.7% (150/173) strains had mutations at rpoB gene; of them, 40% (69/173) strains had mutations at codon S531L of rpoB. The frequency of mutations was not significantly higher in Beijing genotypic MDR strains than in non-Beijing genotypes. Beijing genotypic MDR-TB strains were spreading in Beijing and present a major challenge to TB control in this region. A high prevalence of katG Ser315Thr, inhA promoter region (−15C→T) and rpoB (S531L) mutations was observed. Molecular diagnostics based on gene mutations was a useful method for rapid detection of MDR-TB in Beijing, China.
The aim of the present study was to identify reports of the prevalence of tinnitus in China and to present these findings in a review format.
This study assessed and collated published prevalence estimates of tinnitus and tinnitus severity, creating a narrative synthesis of the data from publications identified from a combination of Chinese and English language databases.
A total of 23 studies were included. Tinnitus prevalence ranged from 4.3 per cent to 51.33 per cent but varied with age and gender. The highest increase in prevalence from previous decade in age occurs during the fifth and sixth decades, and the highest prevalence was in the seventh decade at 32.47 per cent. There is also evidence that tinnitus prevalence is related to certain risk factors including comorbid disorders.
The prevalence of tinnitus in mainland China in this study is consistent with global data. With increasing awareness of the prevalence of tinnitus in China, the development of epidemiological standards is a priority.
The coronavirus disease 2019 (COVID-19) pandemic represents an unprecedented threat to mental health. Herein, we assessed the impact of COVID-19 on subthreshold depressive symptoms and identified potential mitigating factors.
Participants were from Depression Cohort in China (ChiCTR registry number 1900022145). Adults (n = 1722) with subthreshold depressive symptoms were enrolled between March and October 2019 in a 6-month, community-based interventional study that aimed to prevent clinical depression using psychoeducation. A total of 1506 participants completed the study in Shenzhen, China: 726 participants, who completed the study between March 2019 and January 2020 (i.e. before COVID-19), comprised the ‘wave 1’ group; 780 participants, who were enrolled before COVID-19 and completed the 6-month endpoint assessment during COVID-19, comprised ‘wave 2’. Symptoms of depression, anxiety and insomnia were assessed at baseline and endpoint (i.e. 6-month follow-up) using the Patient Health Questionnaire-9 (PHQ-9), Generalised Anxiety Disorder-7 (GAD-7) and Insomnia Severity Index (ISI), respectively. Measures of resilience and regular exercise were assessed at baseline. We compared the mental health outcomes between wave 1 and wave 2 groups. We additionally investigated how mental health outcomes changed across disparate stages of the COVID-19 pandemic in China, i.e. peak (7–13 February), post-peak (14–27 February), remission plateau (28 February−present).
COVID-19 increased the risk for three mental outcomes: (1) depression (odds ratio [OR] = 1.30, 95% confidence interval [CI]: 1.04–1.62); (2) anxiety (OR = 1.47, 95% CI: 1.16–1.88) and (3) insomnia (OR = 1.37, 95% CI: 1.07–1.77). The highest proportion of probable depression and anxiety was observed post-peak, with 52.9% and 41.4%, respectively. Greater baseline resilience scores had a protective effect on the three main outcomes (depression: OR = 0.26, 95% CI: 0.19–0.37; anxiety: OR = 1.22, 95% CI: 0.14–0.33 and insomnia: OR = 0.18, 95% CI: 0.11–0.28). Furthermore, regular physical activity mitigated the risk for depression (OR = 0.79, 95% CI: 0.79–0.99).
The COVID-19 pandemic exerted a highly significant and negative impact on symptoms of depression, anxiety and insomnia. Mental health outcomes fluctuated as a function of the duration of the pandemic and were alleviated to some extent with the observed decline in community-based transmission. Augmenting resiliency and regular exercise provide an opportunity to mitigate the risk for mental health symptoms during this severe public health crisis.
With the increase of access point (AP) density and the exponential growth of mobile devices supported by ultra dense networks (UDNs), overlapped user-centric (UC) clustering is becoming a promising design principle for guaranteeing the quality of service (QoS) required by each UE. However, the overlapped UC clustering has to be jointly designed with resource allocation in UDNs. In this context, both the traffic-load balancing and the limited availability of orthogonal resource blocks (RBs) are carefully considered in UDNs. To tackle these challenges, we formulate a joint overlapped UC clustering and resource allocation problem with the goal of maximizing the system’s spectral efficiency (SE). With the aid of the graph-theoretical framework, the problem is decoupled into two independent subproblems, and a distributed overlapped UC clustering solution as well as a graph-based resource allocation scheme were proposed. Our numerical results quantify the superior performance of the proposed framework in terms of both its per area aggregated user rate (PAAR) and user rate.
Ultra-dense cloud radio access network (UDCRAN) architecture, which integrates the capability of cloud computing and edge computing with the massively deployed radio access points, is a promising solution for the fifth-generation and beyond mobile communications. In order to accommodate the anticipated explosive growth of data traffic, fronthauling technology becomes a challenge technical issue in the fifth-generation and beyond UDCRANs. Moreover, the schemes related to interference management and resource management need to be reconsidered. In this chapter, we will provide a comprehensive review of the current research progress on fronthauling technology. Moreover, we will compare the advantages of various candidate fronthaul schemes.
The wireless edge caching is considered as a promising technique to cope with rapid increase in mobile traffic demand. The fundamental idea of edge caching is to offload the data traffic to local cache memories by dealing with content requests with the pre-fetched contents on network edge nodes. The wireless edge caching consists of two main phases: content placement and content delivery. Since the strategies for these two phases are highly dependent on which devices are capable of caching in the network, the characteristics and types of achievable caching gains appear to vary with the location of cached data. The cached data at the transmitter side can be utilized to reduce the traffic load on backhaul and the latency, while the cached data at the receiver side can be utilized to improve the network resource efficiency and the quality of experience (QoE) of the end-users. This chapter introduces the state-of-the-art wireless edge caching techniques for transmitters and receivers of ultra dense networks and offers a design guideline on reaping the promising gain of wireless edge caching.
Ultra dense networks with directional antennas, like millimetre wave (mmWave) networks, have some promising features about secure communications. This chapter explores the potential of physical layer security in mmWave ultra dense networks. Specifically, we mainly introduced the impact of mmWave channel characteristics, random blockages, and antenna gains on the secrecy performance. Our results reveal that mmWave frequency to high mmWave frequency is demanded to obtain a higher secrecy rate. In addition, new antenna pattern models are needed to well characterize the effective antenna gain for a random interferer seen by the typical receiver when the number of mmWave antennas grows large.
To take full advantage of the ultra-dense architecture and efficiently serve the traffic with spatiotemporal fluctuation, the transmission mechanisms should be redesigned under the constraints of backhaul and energy consumption. In this chapter, we summarize and classify the spatiotemporal arrival properties of different traffic in ultra-dense networks, and optimize several promising technologies to match the traffic. A new approach based on combining stochastic geometry and queueing theory is proposed to provide a useful guidance for the design of ultra-dense networks.
Full duplex ultra-dense network (FDUDN) is envisioned as a promising network paradigm for spectrum efficiency enhancement. This chapter presents a power management scheme, which maximizes the total capacity of FDUDN, under given Quality-of-Service (QoS) and cross-tier interference constraints. The inter-cell power control is formulated as a non-convex optimization problem and the variable substitution is used to transform it into a convex one. Furthermore, the problem is solved through a low-complexity heuristic scheme, which utilizes the water-filling theorem in inter-cell power allocation. Simulation demonstrates the enhancement effect of the proposed scheme in terms of the capacity and the power efficiency.
This chapter investigates the application non-orthogonal multiple access (NOMA) in heterogeneous ultra-dense networks (HUDNs). Particularly, we propose a unified NOMA framework first. Then the applications of the proposed unified NOMA framework in HUDNs will be discussed. With the fact that small cells are densely deployed and the non-orthogonality of resource sharing, the system suffers severe interference. In this chapter, we identify the key challenges in the unified NOMA enabled HUDNs, especially for user association and resource allocation. In addition, we carry out the related case studies for the proposed unified NOMA enabled HUDNs including the user association based on matching theory and resource allocation based on optimization techniques. Furthermore, some critical insights will be provided for the design of NOMA enabled HUDNs, which can promote network access capacity in the next generation of communication systems.
The network densification is one of the prominent solutions for fifth-generation (5G) networks to utilize spectrum resources through intensive deployment of small cells. However, the traffic management in dense networks become a serious challenge for underlying infrastructure supporting the virtual core network. Moreover, 5G will employ different types of communication frameworks: ultra-reliable low latency communication (URLLC), enhanced Mobile Broadband (eMBB), and massive Internet of Things (mIoT). Each identify standard slice type (STT) that have different performance requirements and enabling technologies. The current network developers do not provide any concise identification on how those logic networks would be administrated on top of physical network. This chapter investigates the 5G sliced networks and study virtual networking options to meet the performance requirements of service-based architecture.
Recently, with the development and popularization of unmanned aerial vehicles (UAVs), researches on UAVs have also been attracted increasing attention in wireless communications. By fully exploiting their potentials, leveraging UAVs to assist UDNs can greatly improve the system performance. The probability of having line-of-sight transmissions is higher than the probability in the terrestrial transmissions. Moreover, their attitudes can be freely adjusted. This chapter presents a vision of UAV based UDNs to exploit the potential merits of UAVs in UDNs. The channel characteristics are first discussed. Followed that, the representative scenarios where aerial UAVs are introduced to enhance terrestrial UDNs are investigated in detail, i.e., UAV-enabled BSs, UAV-enabled relays, and UAV-enabled energy transfer. UAV based UDNs also face many challenges, such as the limited spectrum resource and on-board energy. From the spectrum sharing perspective, this chapter also discusses the robust spectrum sharing optimization between UAV communications and terrestrial communications, where the scenarios with abnormal behaviors and uncertain/incomplete information are considered.