Understanding the correlation between topography, species biomass and species life stage would allow forest managers to better foster carbon storage in forests. Using census data from a 60-ha plot in ...south China, we first quantified aboveground biomass (AGB) and how much it varied among different topographies. Next, the specific contribution of 42 dominant species to total aboveground biomass was analyzed for each of the different topographies. We also explored whether these species-topography associations changed, in terms of species’ AGB distribution, during each of the three life stages (sapling, juvenile, adult) for these 42 species. Our results showed that the average AGB was 368.79 Mg ha -1 and that it varied noticeably among the four topographies (Low valley, Slope, High valley and Ridge, which were classified by using fuzzy C-mean clustering based on elevation, convexity, and slope). AGB was significantly lower in the two valleys than in the two other topographies. Of the 42 species, 88.1% showed topographic preferences, and 78.6% appeared to exhibit topographic preferences that changed with life stage. Our work highlights the importance of topography and life stage in species biomass distribution and suggests that different combinations of species and life stages, based on species topographic preferences across life stages, may be better suited in different tropical rainforest topographies to maximize carbon storage overall.
Numerous reforestation projects have been conducted to improve soil fertility in degraded forests, often causing alterations to the soil microbial communities. However, it remains unclear whether ...microbial functional groups are affected and how these groups correlate with an increase in the nutrient contents during reforestation. We investigated the abundance and composition of free-living nitrogen-fixing microorganisms (diazotrophs) by quantifying and sequencing the marker gene
in bulk soils from five reforestation approaches, including legumes and non-legumes, in subtropical China. The relationships between diazotrophic community attributes and soil nitrogen (N) content NO
, NH
, and microbial biomass N (MBN) were examined under various approaches. Abundance of diazotrophs was highest in the native tree plantation (
spp. and
) and
monoculture (AM), and lowest in the
monoculture. The diazotrophic abundance correlated positively with soil organic matter and water content while there was a negative correlation to pH. The composition of diazotrophic community differed significantly among the five reforestation approaches examined and was closely correlated with variations in soil pH, NH
and water content. Diazotrophic community composition was closely related to soil NH
content, whereas abundance was not. The AM contained higher NH
, NO
and MBN contents than the other reforestation approaches, which may be associated with the indicator species of diazotrophs (
,
, and
). However, there were more indicator species of
in the mixed
plantation (
and
) than in AM, which might have contributed to the remarkedly lower N content compared to AM. Overall, the soil N content under reforestation appeared to be more related to the composition of diazotroph community than to the abundance of diazotrophs.
Dielectric Relaxations in Rutile TiO2 Wang, Chunchang; Zhang, Nan; Li, Qiuju ...
Journal of the American Ceramic Society,
January 2015, Letnik:
98, Številka:
1
Journal Article
Recenzirano
Dielectric properties of high‐purity (4N degree) rutile TiO2 ceramics were investigated over a wide temperature (100–1073 K) and frequency (20 Hz–10 MHz) ranges. X‐ray photoemission spectroscopy ...measurement revealed the sample possesses mixed‐valent states of Ti3+/Ti4+. Four thermally activated relaxations were observed. The lowest temperature relaxation (R1) features two Arrhenius segments with activation energy of 30 and 80 meV for the low‐ and high‐temperature segments, respectively. This relaxation was argued to be a polaron relaxation due to electrons hopping between Ti3+ and Ti4+ ions. The second relaxation (R2) appears around room temperature showing activation energy of 0.68 eV is believed to be a Maxwell‐Wagner relaxation. The high‐temperature relaxations R3 and R4 with activation energy of 0.84 and 1.26 eV were ascribed to the conduction process due to the hopping motions of singly and doubly charged oxygen vacancies, respectively.
Graphite has been the major anode material of choice for lithium-ion batteries (LIBs) for over 30 years. This study reports three-dimensional (3D) printing of comb-like 3D natural graphite (NG) ...electrodes for high-performance interdigitated 3D LIBs. Printable NG inks were developed and 3D NG electrodes with the thickness of 347.3 μm, 581.7 μm and 786.7 μm (corresponding areal mass loading: 16.3 mg cm−2, 24.4 mg cm−2 and 32.9 mg cm−2) were fabricated via a low temperature direct write 3D printing technology. The 3D-printed electrodes had tri-modally hierarchical porous microstructures with a high porosity of 54.84%. In addition, these thick electrodes showed excellent electrochemical performance with an impressive areal capacity of 13.68 mAh cm−2 @ 0.1C for electrodes with the thickness of 786.7 μm. With this type of 3D electrodes, the capacity fade over the increase of discharge rates was greatly reduced in comparison with tape casted electrodes with the same electrode thickness. This study demonstrates the potential of 3D-printed NG electrodes for high-performance LIBs.
Significance Nitrogen (N) losses from terrestrial ecosystems can occur as inert forms or heat-trapping greenhouse gases, and via nitrate (NO ₃⁻) leaching to drainage waters, which can contribute to ...eutrophication and anoxia in downstream ecosystems. Here, we use natural isotopes to demonstrate that microbial gaseous N production via denitrification is the dominant pathway of NO ₃⁻ removal from forest ecosystems, with gaseous N losses that are up to ∼60-fold higher than those based on traditional techniques. Denitrification becomes less efficient compared with NO ₃⁻ leaching in more N-polluted ecosystems, which has important implications for assessing the connections between terrestrial soils and downstream ecosystems under rising anthropogenic N deposition.
Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N ₂) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO ₃⁻) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6–30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO ₃⁻ leaching, pointing to widespread dominance of denitrification in removing NO ₃⁻ from forest ecosystems across a range of conditions. Further, we report that the loss of NO ₃⁻ to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.
Bacteria are the highest abundant microorganisms in the soil. To investigate bacteria community structures, diversity, and functions, contrasting them in four different seasons all the year round ...with/within two different forest type soils of China. We analyzed soil bacterial community based on 16S rRNA gene sequencing via Illumina HiSeq platform at a temperate deciduous broad-leaved forest (Baotianman, BTM) and a tropical rainforest (Jianfengling, JFL). We obtained 51,137 operational taxonomic units (OTUs) and classified them into 44 phyla and 556 known genera, 18.2% of which had a relative abundance >1%. The composition in each phylum was similar between the two forest sites.
and
were the most abundant phyla in the soil samples between the two forest sites. The Shannon index did not significantly differ among the four seasons at BTM or JFL and was higher at BTM than JFL in each season. The bacteria community at both BTM and JFL showed two significant (
< 0.05) predicted functions related to carbon cycle (anoxygenic photoautotrophy sulfur oxidizing and anoxygenic photoautotrophy) and three significant (
< 0.05) predicted functions related to nitrogen cycle (nitrous denitrificaton, nitrite denitrification, and nitrous oxide denitrification). We provide the basis on how changes in bacterial community composition and diversity leading to differences in carbon and nitrogen cycles at the two forests.
•Stable SOC was mainly distributed at hillside and valley in the tropical rainforest.•Terrain explained the most spatial variations of SOC and its stability fractions.•Abiotic factors explained more ...variations of SOC fractions than biotic factors.•Terrain should be considered in the SOC estimation and related biogeochemical model.
Estimation of soil organic carbon (SOC) storage and its dynamics in tropical montane forests is crucial for climate change prediction, which calls for further investigation into the spatial variation in SOC and its stability mechanisms. In this study, 60 subplots (20 m × 20 m) were randomly selected within a 60 ha tropical montane rainforest dynamic monitoring plot located in southern China. The physical (HFC and LFC) and chemical fractions of SOC (alkyl C, O-alkyl C, aromatic C and carbonyl C), microbial biomass carbon and other soil properties at depths of 0–10 cm, plant species and root biomass (0–10 cm and 10–20 cm) were investigated. Geostatistical methods, multiple regression trees and redundant analysis were used to reveal that the spatial variations in SOC and its stability mechanisms with the terrain. The results show that the spatial variations in HFC and the ratios of alkyl carbon/O-alkyl carbon had a moderate spatial dependence due to the complex terrain. High SOC and its physical stability fractions (HFC) were distributed along ridgelines, while the chemical stability index of SOC (alkyl C/O-alkyl C) was the highest on hillsides and in valleys. Terrain convexity best explained the spatial variations in SOC and HFC, while total nitrogen and convexity together best explained the spatial variation in the chemical fractions of SOC. Abiotic factors explained more of the variation in SOC and its fractions than biotic factors, while abiotic and biotic factors were covariant. The specific factors controlling the distribution of SOC and its fractions differed with the types of micro-terrain. These results highlight the influence of terrain on the distribution and accumulation of SOC in tropical forest ecosystems. Hence, terrain should be considered a key factor in biogeochemical models.
Acute heart failure necessitates intensive care, and arterial catheterization is a commonly performed invasive procedure in the intensive care unit (ICU). We aimed to investigate the association ...between arterial catheterization and outcomes in acute heart failure patients without shock.
We utilized MIMIC-IV database records for acute heart failure patients at Beth Israel Deaconess Medical Center from 2008 to 2019. Employing doubly robust estimation, we examined the relationship between arterial catheterization and outcomes, including 28-day, 90-day, in-hospital mortality, and ICU-free days within 28 days.
Of 6936 patients identified, 2078 met inclusion criteria; 347 underwent arterial catheterization during their ICU stay. We observed no significant difference in 28-day mortality (odds ratio OR: 0.61, 95 % confidence interval CI: 0.31–1.21, P = 0.155), though catheterization was associated with reduced in-hospital mortality (OR: 0.41, 95 % CI: 0.14–0.65, P = 0.02). No significant effects were observed on 90-day mortality or ICU-free days within 28 days.
Our findings suggest that arterial catheterization is not associated with 28- and 90-day mortality rates in acute heart failure patients without shock but is linked to lower in-hospital mortality. Additional research and consensus are required to determine the appropriate utilization of arterial catheterization in patients.
Objective
Sepsis is the leading cause of death in patients admitted to adult intensive care units (ICUs). We aimed to determine the predictive value of red blood cell distribution width (RDW) in ...patients with sepsis in a large cohort.
Methods
This retrospective observational study used data from the eICU Collaborative Research Database. The prognostic value of RDW was investigated using the receiver operating characteristic (ROC) curve, multiple logistic regression model, integrated discriminatory index (IDI), and net reclassification index (NRI).
Results
In total, 9743 patients were included. The area under the ROC curve of the RDW for predicting hospital mortality was 0.631 (95% confidence interval CI: 0.616–0.645). Based on the multiple logistic regression model, an RDW of ≥14.5% was correlated with hospital mortality, regardless of Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation IV (APACHE IV) scores (odds ratio OR: 1.838, 95% CI: 1.598–2.119). Using SOFA and APACHE IV scores as reference, the IDI and continuous NRI of RDW for hospital mortality was about 0.3 and 0.014, respectively.
Conclusions
The RDW may be useful in predicting hospital mortality in patients with sepsis, offering extra prognostic value beyond SOFA and APACHE IV scores.
Acute heart failure is a serious condition. Atrial fibrillation is the most frequent arrhythmia in patients with acute heart failure. The occurrence of atrial fibrillation in heart failure patients ...worsens their prognosis and leads to a substantial increase in treatment costs. There is no tool that can effectively predict the onset of atrial fibrillation in patients with acute heart failure in the ICU currently.
We retrospectively analyzed the MIMIC-IV database of patients admitted to the intensive care unit (ICU) for acute heart failure and who were initially sinus rhythm. Data on demographics, comorbidities, laboratory findings, vital signs, and treatment were extracted. The cohort was divided into a training set and a validation set. Variables selected by LASSO regression and multivariate logistic regression in the training set were used to develop a model for predicting the occurrence of atrial fibrillation in acute heart failure in the ICU. A nomogram was drawn and an online calculator was developed. The discrimination and calibration of the model was evaluated. The performance of the model was tested using the validation set.
This study included 2342 patients with acute heart failure, 646 of whom developed atrial fibrillation during their ICU stay. Using LASSO and multiple logistic regression, we selected six significant variables: age, prothrombin time, heart rate, use of vasoactive drugs within 24 h, Sequential Organ Failure Assessment (SOFA) score, and Acute Physiology Score (APS) III. The C-index of the model was 0.700 (95% CI 0.672-0.727) and 0.682 (95% CI 0.639-0.725) in the training and validation sets, respectively. The calibration curves also performed well in both sets.
We developed a simple and effective model for predicting atrial fibrillation in patients with acute heart failure in the ICU.
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