| 340571. |
- Huang, Kun, et al.
(author)
-
Enhanced peak growth of global vegetation and its key mechanisms
- 2018
-
In: Nature Ecology and Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:12, s. 1897-1905
-
Journal article (peer-reviewed)abstract
- The annual peak growth of vegetation is critical in characterizing the capacity of terrestrial ecosystem productivity and shaping the seasonality of atmospheric CO2 concentrations. The recent greening of global lands suggests an increasing trend of terrestrial vegetation growth, but whether or not the peak growth has been globally enhanced still remains unclear. Here, we use two global datasets of gross primary productivity (GPP) and a satellite-derived Normalized Difference Vegetation Index (NDVI) to characterize recent changes in annual peak vegetation growth (that is, GPPmax and NDVImax). We demonstrate that the peak in the growth of global vegetation has been linearly increasing during the past three decades. About 65% of the NDVImax variation is evenly explained by expanding croplands (21%), rising CO2 (22%) and intensifying nitrogen deposition (22%). The contribution of expanding croplands to the peak growth trend is substantiated by measurements from eddy-flux towers, sun-induced chlorophyll fluorescence and a global database of plant traits, all of which demonstrate that croplands have a higher photosynthetic capacity than other vegetation types. The large contribution of CO2 is also supported by a meta-analysis of 466 manipulative experiments and 15 terrestrial biosphere models. Furthermore, we show that the contribution of GPPmax to the change in annual GPP is less in the tropics than in other regions. These multiple lines of evidence reveal an increasing trend in the peak growth of global vegetation. The findings highlight the important roles of agricultural intensification and atmospheric changes in reshaping the seasonality of global vegetation growth.
|
|
| 340572. |
- Huang, Ketuan, et al.
(author)
-
Genetic variants and Expression of Cytochrome p450 Oxidoreductase Predict Postoperative Survival in Patients with Hepatitis B Virus-Related Hepatocellular Carcinoma
- 2019
-
In: Journal of Cancer. - : IVYSPRING INT PUBL. - 1837-9664. ; 10:6, s. 1453-1465
-
Journal article (peer-reviewed)abstract
- Our current study investigates the prognostic values of genetic variants and mRNA expression of cytochrome p450 oxidoreductase (POR) in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). A total of 19 candidate single nucleotide polymorphisms (SNPs) located in the exons of POR were genotyped using Sanger sequencing from 476 HBV-related HCC patients who underwent hepatectomy between 2003 and 2013. The mRNA expression of POR in 212 patients with HBV-related HCC was obtained from GSE14520 dataset. Survival analysis was performed to investigate the association of POR variants and mRNA expression with overall survival (OS) and recurrence-free survival (RFS). Nomograms were used to predict the prognosis of HBV-related HCC patients. Gene set enrichment analysis (GSEA) was used to investigate the mechanism of POR in HBV-related HCC prognosis. The polymorphism POR-rs1057868 was significantly associated with HBV-related HCC OS (CT/TT vs. CC, hazard ratio [HR] = 0.69, 95% confidence interval [CI] = [0.54, 0.88], P = 0.003), but not significantly associated with RFS (CT/TT vs. CC, P = 0.378). POR mRNA expression was also significantly associated with HBV-related HCC OS (high vs. low, HR = 0.61, 95% CI = [0.38, 0.97], P= 0.036), but not significantly associated with the RFS (high vs. low, P = 0.201). Two nomograms were developed to predict the HBV-related HCC OS. Furthermore, GSEA suggests that multiple gene sets were significantly enriched in liver cancer survival and recurrence, as well as POR-related target therapy in the liver. In conclusion, our study suggests that POR-rs1057868 and mRNA expression may serve as a potential postoperative prognosis biomarker in HBV-related HCC.
|
|
| 340573. |
- Huang, K, et al.
(author)
-
Impact of alternative reimbursement strategies in the new cooperative medical scheme on caesarean delivery rates : A mixed-method study in rural China
- 2012
-
In: BMC Health Services Research. - : Springer Science and Business Media LLC. - 1472-6963. ; 12:1, s. Article number 217-
-
Journal article (peer-reviewed)abstract
- Background: The rate of caesarean delivery (CD) in rural China has been rapidly increasing in recent decades. Due to the exorbitant costs associated with CD, paying for this expensive procedure is often a great challenge for the majority of rural families. Since 2003, the Chinese government has re-established the NewCooperative Medical Scheme (NCMS), aimed to improve the access of essential healthcare to rural residents and reduce financial burden owing to high out of pocket payments. This paper seeks to test the hypothesis that NCMS may provide service users and providers with financial incentives to select CD. It also assesses the effect of different health insurance reimbursement strategies of NCMS on CD rates in rural China. Methods: Mixed quantitative and qualitative methods were adopted for data collection. Two cross-sectional household surveys were conducted with women having babies delivered in 2006 and 2009; 2326 and 1515 women, respectively, from the study sites were interviewed using structured questionnaires, to collect demographic and socio-economic data, maternal and child care characteristics and health-related expenditures. Focus group discussions (FGDs) and in-depth key informant interviews (KIIs) were undertaken with policy makers, health managers, providers and mothers to understand their perceptions of the influence of NCMS on the choices of delivery mode. Results: The CD rates in the two study counties were 46.0 percent and 64.7 percent in 2006, increasing to 63.6 percent and 82.1 percent, respectively, in 2009. The study found that decisions on the selection of CD largely came from the pregnant women. Logistic regression analysis, after adjusting for socio-economic, maternal and fetal characteristics, did not indicate a significant effect of either proportional reimbursement or fixed amount reimbursement on the choice of CD for both study years. Interviews with stakeholders reflected that different reimbursable rates for CD and vaginal deliveries did not have a significant effect on controlling the rising CD rate in the study countries. Conclusion: NCMS reimbursement strategies adopted in the study counties of China did not have a significant effect on the selection of CD for babydeliveries. The rapid rise of the CD rates of rural China has remained a serious issue. Other effective measures, such as health education to increase awareness of mothers' knowledge, an improving training of health staff in evidence-based delivery care, maybe could do more to promote rational baby delivery in rural China.
|
|
| 340574. |
- Huang, Kai, et al.
(author)
-
Numerical study of the influence of the thermal gas expansion on the boundary layer flame flashback in channels with different wall thermal conditions
- 2023
-
In: Energies. - : MDPI. - 1996-1073. ; 16:4
-
Journal article (peer-reviewed)abstract
- In recent years, boundary layer flame flashback (BLF) has re-emerged as a technological and operational issue due to the more widespread use of alternative fuels as a part of a global effort to promote carbon neutrality. While much understanding has been achieved in experiments and simulations of BLF in the past decades, the theoretical modeling of BLF still largely relies on the progress made as early as the 1940s, when the critical gradient model (CGM) for the laminar flame flashback was proposed by Lewis and von Elbe. The CGM does not account for the modification of the upstream flow by the flame, which has been recently shown to play a role in BLF. The aim of the present work is to gain additional insight into the effects of thermal gas expansion and confinement on the flame-flow interaction in laminar BLF. Two-dimensional simulations of the confined laminar BLF in a channel are performed in this work. The parametric study focuses on the channel width, the thermal gas expansion coefficient, and the heat losses to the wall. This study evaluates the influence of these factors on the critical condition for the flame flashback. By varying the channel width, it is demonstrated that at the critical condition, the incoming flow in narrow channels is modified globally by the thermal gas expansion, while in wider channels, the flow modification by the flame tends to be more local. In narrow channels, a non-monotonic dependence of the critical-condition centerline velocity on the channel width has been identified. The variation of the heat loss to the wall confirms that the wall’s thermal conditions can significantly alter the flashback limit, with the flashback propensity being larger when the thermal resistance of the wall is high. To assess the general applicability of the CGM, the flame consumption speed and the flow velocity near the wall are quantified. The results confirm that the assumption of flame having no influence on the upstream flow, employed in the CGM, is not fulfilled under confinement for a realistic thermal gas expansion. This results in a general disagreement between the simulations and the CGM, which implies that the thermal expansion effects should be accounted for when considering the confined boundary layer flashback limits. It is shown that the critical velocity gradient increases with the gas expansion coefficient for the given channel width and wall thermal condition.
|
|
| 340575. |
- Huang, Kai, et al.
(author)
-
Protected excitation-energy reservoir for efficient upconversion luminescence
- 2017
-
In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 10:1, s. 250-259
-
Journal article (peer-reviewed)abstract
- Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the general low luminescence intensity of UCNPs and inefficient energy transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low efficiency issue by developing versatile core-shell nanostructures, where high-concentration sensitizers and activators are confined in the core- and shell region, representatively for hexagonal NaYF4:Yb, Er UCNPs. After doping concentration optimization, the sensitizer-rich core, is able to harvest/accumulate more excitation energy and generate almost one order of magnitude higher luminescence intensity than conventional homogeneously doped nanostructures. At the same time, the activator ions located in the shell enable a ~6 times more efficient resonant energy transfer from UCNPs to surface-bound acceptor dye molecules due to the short distance between donor-acceptor pairs. Our work provides new insights into the rational design of UCNPs and will greatly increase the general applicability of upconversion nanotechnologies.
|
|
| 340576. |
|
|
| 340577. |
|
|
| 340578. |
- Huang, Kaibin, et al.
(author)
-
Simultaneous Information and Power Transfer for Broadband Wireless Systems
- 2013
-
In: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 61:23, s. 5972-5986
-
Journal article (peer-reviewed)abstract
- Far-field microwave power transfer (MPT) will free wireless sensors and other mobile devices from the constraints imposed by finite battery capacities. Integrating MPT with wireless communications to support simultaneous wireless information and power transfer (SWIPT) allows the same spectrum to be used for dual purposes without compromising the quality of service. A novel approach is presented in this paper for realizing SWIPT in a broadband system where orthogonal frequency division multiplexing and transmit beamforming are deployed to create a set of parallel sub-channels for SWIPT, which simplifies resource allocation. Based on a proposed reconfigurable mobile architecture, different system configurations are considered by combining single-user/multi-user systems, downlink/uplink information transfer, and variable/fixed coding rates. Optimizing the power control for these configurations results in a new class of multi-user power-control problems featuring the circuit-power constraints, specifying that the transferred power must be sufficiently large to support the operation of the receiver circuitry. Solving these problems gives a set of power-control algorithms that exploit channel diversity in frequency for simultaneously enhancing the throughput and the MPT efficiency. For the system configurations with variable coding rates, the algorithms are variants of water-filling that account for the circuit-power constraints. The optimal algorithms for those configurations with fixed coding rates are shown to sequentially allocate mobiles their required power for decoding in ascending order until the entire budgeted power is spent. The required power for a mobile is derived as simple functions of the minimum signal-to-noise ratio for correct decoding, the circuit power and sub-channel gains.
|
|
| 340579. |
- Huang, Ke, et al.
(author)
-
The confounding effect of snow cover on assessing spring phenology from space : A new look at trends on the Tibetan Plateau
- 2021
-
In: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 756
-
Journal article (peer-reviewed)abstract
- The Tibetan Plateau is the highest and largest plateau in the world, hosting unique alpine grassland and having a much higher snow cover than any other region at the same latitude, thus representing a “climate change hot-spot”. Land surface phenology characterizes the timing of vegetation seasonality at the per-pixel level using remote sensing systems. The impact of seasonal snow cover variations on land surface phenology has drawn much attention; however, there is still no consensus on how the remote sensing estimated start of season (SOS) is biased by the presence of preseason snow cover. Here, we analyzed SOS assessments from time series of satellite derived vegetation indices and solar-induced chlorophyll fluorescence (SIF) during 2003–2016 for the Tibetan Plateau. We evaluated satellite-based SOS with field observations and gross primary production (GPP) from eddy covariance for both snow-free and snow covered sites. SOS derived from SIF was highly correlated with field data (R2 = 0.83) and also the normalized difference phenology index (NDPI) performed well for both snow free (R2 = 0.77) and snow covered sites (R2 = 0.73). On the contrary, normalized difference vegetation index (NDVI) correlates only weakly with field data (R2 = 0.35 for snow free and R2 = 0.15 for snow covered sites). We further found that an earlier end of the snow season caused an earlier estimate of SOS for the Tibetan Plateau from NDVI as compared to NDPI. Our research therefore adds new evidence to the ongoing debate supporting the view that the claimed advance in land surface SOS over the Tibetan Plateau is an artifact from snow cover changes. These findings improve our understanding of the impact of snow on land surface phenology in alpine ecosystems, which can further improve remote sensing based land surface phenology assessments in snow-influenced ecosystems.
|
|
| 340580. |
- Huang, Kaicheng, et al.
(author)
-
Tipping point of a conifer forest ecosystem under severe drought
- 2015
-
In: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 10:2
-
Journal article (peer-reviewed)abstract
- Drought-induced tree mortality has recently received considerable attention. Questions have arisen over the necessary intensity and duration thresholds of droughts that are sufficient to trigger rapid forest declines. The values of such tipping points leading to forest declines due to drought are presently unknown. In this study, we have evaluated the potential relationship between the level of tree growth and concurrent drought conditions with data of the tree growth-related ring width index (RWI) of the two dominant conifer species (Pinus edulis and Pinus ponderosa) in the Southwestern United State (SWUS) and the meteorological drought-related standardized precipitation evapotranspiration index (SPEI). In this effort, we determined the binned averages of RWI and the 11 month SPEI within the month of July within each bin of 30 of RWI in the range of 0–3000.Wefound a significant correlation between the binned averages of RWI and SPEI at the regional-scale under dryer conditions. The tipping point of forest declines to drought is predicted by the regression model as SPEItp = −1.64 and RWItp = 0, that is, persistence of the water deficit (11 month) with intensity of −1.64 leading to negligible growth for the conifer species. When climate conditions are wetter, the correlation between the binned averages ofRWI and SPEI is weaker which we believe is most likely due to soil water and atmospheric moisture levels no longer being the dominant factor limiting tree growth.Wealso illustrate a potential application of the derived tipping point (SPEItp = −1.64) through an examination of the 2002 extreme drought event in theSWUSconifer forest regions. Distinguished differences in remote-sensing based NDVI anomalies were found between the two regions partitioned by the derived tipping point.
|
|
