خيارات البحث
النتائج 5101 - 5110 من 6,453
Evaluating CO2 flux and recharge source in geothermal springs, Garhwal Himalaya, India: stable isotope systematics and geochemical proxies النص الكامل
2020
Tiwari, Sameer K. | Gupta, Anil K. | Asthana, A. K. L.
Evaluation of geogenic carbon fluxes between solid Earth and its atmosphere is essential to understand the global geological carbon cycle. Some of the key geogenic CO₂ suppliers are the magmatic mantle and metamorphic degassing from active and quiescent volcanoes, fault zones, geothermal systems and CO₂ rich groundwater. Indian Himalayan geothermal field hosts about 340 geothermal springs in natural as well as artesian condition that eject hot waters and volatiles with varied temperature and chemical composition. These sites provide an opportunity to analyse tectonically driven gas emissions and their impact on regional and global climate. Here we adopt a method for direct measurement of Dissolved Inorganic Carbon (DIC ≈ HCO₃) concentration in the geothermal springs to estimate geogenic CO₂ flux from an active region based on water discharge and area of geothermal system between the tectonic boundaries of the Main Central Thrust (MCT) and Main Boundary Thrust (MBT) of the Garhwal (Northwest) Himalaya. In the study area, geothermal spring water contain high δ¹³CDIC ratio (− 8.5‰ to + 4.0‰ VPDB), and among the major ions, bicarbonate (HCO₃⁻) varies by an order of magnitude from 1697 to 21,553 μEq/L; chloride and sodium vary from 90 to 19,171 μEq/L and 436 to 23181 μEq/L. The elevated concentration of Cl⁻ and Na⁺ in geothermal spring waters suggests affinity towards their deeper origin. These geothermal springs cover a large area of nearly 10,000 km² of the Garhwal region showing a significant discharge of CO₂ rich water with an estimated carbon dioxide degassing flux of ~7.2 × 10⁶ mol/year to the atmosphere. Considering widespread occurrences of geothermal springs in tectonically active areas worldwide, the proposed direct measurement of DIC may be used as a reliable tool to estimate CO₂ fluxes in different active orogenic settings within the Earth system. Results of stable isotopes of δ¹⁸O ₍VSMOW₎ and δD ₍VSMOW₎ in these geothermal spring waters follow the Global Meteoric Water Line (GMWL), suggesting affinity of their recharge through the meteoric origin.
اظهر المزيد [+] اقل [-]SLC16A1-AS1 enhances radiosensitivity and represses cell proliferation and invasion by regulating the miR-301b-3p/CHD5 axis in hepatocellular carcinoma النص الكامل
2020
Pei, Shenglin | Chen, Zuyi | Tan, Huajun | Fan, Liwei | Zhang, Baina | Zhao, Chang
Hepatocellular carcinoma (HCC), a common type of human malignancies, leads to increasing incidence and fairly high mortality. An increasing number of studies have verified that long noncoding RNAs (lncRNAs) played key roles in the development of multiple human cancers. As a biomarker, SLC16A1-AS1 has been reported in non-small cell lung cancer (NSCLC) and oral squamous cell carcinoma (OSCC). Thus, we decided to investigate whether SLC16A1-AS1 exerts its biological function in HCC. In this study, we discovered that SLC16A1-AS1 was obviously downregulated in HCC tissues and cells. Overexpression of SLC16A1-AS1 inhibited HCC cell proliferation, invasion, and epithelial-mesenchymal transition (EMT) process as well as promoted cell apoptosis. Moreover, SLC16A1-AS1 was confirmed to enhance the radiosensitivity of HCC cells. Molecular mechanism exploration suggested that SLC16A1-AS1 served as a sponge for miR-301b-3p and CHD5 was the downstream target gene of miR-301b-3p in HCC cells. Rescue assays implied that CHD5 knockdown could recover the effects of SLC16A1-AS1 overexpression on HCC cellular processes. In brief, our study clarified that SLC16A1-AS1 acted as a tumor suppressor in HCC by targeting the miR-301b-3p/CHD5 axis, which may be a promising diagnostic biomarker and provide promising treatment for HCC patients.
اظهر المزيد [+] اقل [-]Chemical characterization of mountain forest soils: impact of long-term atmospheric deposition loadings (Czech–Polish–German border region) النص الكامل
2020
Havelcová, Martina | Machovič, Vladimír | Novák, František | Lapčák, Ladislav | Mizera, Jiří | Hendrych, Jiří
The composition of lipids in soil offers clues to soil degradation processes due their persistency and selectivity in soil, and close relation to long-term processes in the ecosystem, thanks to their role in cell membranes of organisms. Organic solvent-extractable compounds were recovered from soils collected at two sites differing in the degree of forest damage. Gas chromatography/mass spectroscopy and Fourier transform infrared spectroscopy were applied in order to characterize solvent-extractable lipids. Raman spectroscopy was also applied as it provides distinct advantages for determining the structural order of carbonaceous materials. The organic matter measurement techniques were combined with an established simultaneous multi-element measurement technique. Variations in individual soil horizons from the sites were reflected in the crystallinity of epicuticular waxes, presence of long-chain aliphatic hydrocarbons, concentrations of n-alkanes, saturated and unsaturated fatty acids, dicarboxylic acids, and in the content of aromatic structures, hydroxyl, ester, and carboxylic acid groups. The results are explained by differently transformed organic matter. The concentrations of elements in the soils were also affected by atmospheric depositions, including higher accumulations of arsenic and antimony, and lower contents of natural nutrients. These data have potential to be used as sensitive biogenic indicators of ecosystem damage by long-term atmospheric depositions.
اظهر المزيد [+] اقل [-]Adsorption-desorption and co-migration of vanadium on colloidal kaolinite النص الكامل
2020
Yang, Jin-yan | Luo, Hou-qiao | Zhu, Yan-yuan | Yu, Ya-qi | He, Wen-yan | Wu, Zhen-zhong | Wang, Bin
Vanadium (V) pollution in soil has been widely noted, while knowledge about the effect of soil colloid on migration of V is scarce. Batch adsorption-desorption and transportation of the colloid-adsorbed V in columns packed with quartz sand under various environment conditions were carried out to explore the retention and transportation of V by colloidal kaolinite. Batch adsorption-desorption studies show that the adsorption of V by the colloidal kaolinite was mainly specific adsorption and redox played a limited role in the adsorption process. The maximum adsorption capacity of the colloidal kaolinite was 712.4 mg g⁻¹, and about 5.9–8.7% of the adsorbed V could be desorbed. Both the adsorption-desorption and migration of V with colloidal kaolinite were highly ambient condition dependent. The column studies show that V was highly mobile in the saturated porous media. An easier transfer of V with an increase in pH, IS, and velocity of flow was noted. However, the increase of IS lead to the blockage of the colloidal kaolinite transportation. The recovery rate of the colloidal kaolinite at pH 7 and 9 was 2.0 and 2.1 times that at pH 5, respectively. The migration of colloidal-adsorbed V in sand column preceded that of V ion, but more colloidal-bound V than V ion remained in the column. Lack of consideration of the combination and co-transportation of V and colloidal kaolinite will lead to an overestimation of the risk of V to deeper soil profiles and groundwater. Graphical abstract
اظهر المزيد [+] اقل [-]Date palm fruit extract ameliorated pancreatic apoptosis, endocrine dysfunction and regulatory inflammatory cytokines in Streptozotocin-induced diabetes in rats النص الكامل
2020
Hafez, Mona H. | Elblehi, Samar S. | El-Sayed, Yasser S.
The current work studied the mechanism(s) and ability by which date palm (Phoenix dactylifera L.) fruit extract (DPE) inspired a glucose-lowering impact in rats suffering from diabetes. Forty-eight albino rats were divided into six various experimental treatments after induction of diabetes by intraperitoneal infusion of streptozotocin (45 mg/kg bwt) as follows: normal control, DPE, diabetic control, diabetic glibenclamide (GLI), diabetic DPE, and diabetic GLI plus DPE-treated groups. In animals euthanized after 8 weeks, blood and pancreatic tissue samples were assembled to assess different biochemical and histopathological changes. The expressions of insulin, B cell lymphoma-2 (Bcl-2), and cysteine aspartate-specific protease-3 (caspase-3) in islet β cells were also evaluated using immunohistochemical assessment. Diabetic rats exhibited hyperglycemia; increment of pancreatic malondialdehyde (lipid peroxidation biomarker), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β); and decrement of plasma insulin and pancreatic antioxidants: glutathione, superoxide dismutase, and catalase values. Also, the pancreatic islets exhibited histopathological and morphometric alternations associated with weak positive insulin and Bcl-2 immunoreactivity and strong positive caspase-3 immunoreactivity. DPE and/or GLI, an anti-diabetic drug, improved the pancreatic histoarchitecture and improved β cell function and structure, which increased insulin levels and improved the insulin, Bcl-2, and caspase-3 immunoreactivity in diabetic rats. Nevertheless, the combined DPE and GLI therapy revealed a significant recovery and restoration of β cells’ structure and function. The date palm fruit has anti-apoptotic, anti-inflammatory, and antioxidant activities and hypoglycemic effects, which in turn play a pivotal role in avoiding the progression of diabetes mellitus. Moreover, it could potentiate the glucose-lowering activity of anti-diabetic drugs.
اظهر المزيد [+] اقل [-]Examining the impact of polycentric urban form on air pollution: evidence from China النص الكامل
2020
Meichang, Wang | Bingbing, Zhang
Numerous studies on megacities have reported less air pollution in polycentric form urban than monocentric form urban. However, findings from these studies do not imply that increasing air pollution in region or country is accompanied by the expanding megacities. Using satellite night-light data, this study investigates the impact of polycentric urban form at the provincial level on PM₂.₅ concentrations in China while controlling for variables of urban population size, energy consumption, and the weather. The results reveal that the PM₂.₅ concentrations are reduced by 1.46% to 2.67%, with a 1% increase in polycentric urban form. The similar impact has also been observed in the South China, but larger in the Central China. Further studies show that the urban form-air pollution relationship mainly influenced by transportation distance and enhanced by rising per capita income. The findings suggest that regional planning and policies favoring polycentric urban patterns should be strengthened to alleviate air pollution.
اظهر المزيد [+] اقل [-]Modification of epoxy groups of poly(hydroxylmethyl methacrylate-co-glycidyl methacrylate) cryogel with H3PO4 as adsorbent for removal of hazardous pollutants النص الكامل
2020
Bayramoglu, Gulay | Arica, Mehmet Yakup
Poly(hydroxylmethyl methacrylate-co-glycidyl methacrylate) (p(HEMA-GMA)) macroporous cryogel with high density of epoxy groups was synthesized, and the epoxy groups of the cryogel were modified into phosphonate groups. The effects of dye concentrations, adsorption time, pH, salt concentration, and adsorption temperature on the adsorption of Direct Blue-53 (DB-53) and Reactive Blue-160 (RB-160) dyes were studied. The maximum adsorption capacity was found to be 245.3 and 155.8 mg/g (0.255 or 0.119 mmol/g) for the DB-53 and RB-160 dyes, respectively. The higher adsorption capacity achieved for the DB-53 compared with the RB-160 dye can result from the pendant primary amino groups of the DB-53 dye as well as the smaller size of the dye molecule. The Langmuir isotherm model and the pseudo-second-order kinetic model well described the experimental data. The p(HEMA-GMA)-PO₄²⁻ adsorbent has many operational advantages for the removal of pollutants. It could be a promising adsorbent to be used in industrial wastewater treatment.
اظهر المزيد [+] اقل [-]Global characteristics and trends of research on construction dust: based on bibliometric and visualized analysis النص الكامل
2020
Guo, Ping | Tian, Wei | Li, Huimin | Zhang, Guangmin | Li, Jianhui
The booming construction industry has led to many environmental and occupational health and safety problems. Construction dust caused irreversible damage to the health of frontline workers and polluted the surrounding air environment, which has attracted the attention of researchers and practitioners. In this study, to systematically sort and analyze the distribution of construction dust (CD) research, its hot areas, and the evolution of its fronts, papers with “construction dust” as the subject term in the Web of Science Core Collection Database since 2010 are visually analyzed using CiteSpace. The characteristics of these papers, including the quantity trend, quality, author group, affiliated institution type, and journal type, are summarized, and keyword co-appearance and paper co-citation knowledge maps are produced. The results show that (1) China is the backbone of CD research, and the research results account for a considerable proportion of the total. (2) Respiratory dust and atmospheric aerosols, marble dust, PM₂.₅, and other hot issues have always attracted international attention. And exposure assessment and spatial distribution were the main focuses in the study of CD. (3) The direction of CD research will explore in a more subtle and intelligent direction in the future, for example, monitoring and control equipment under the technical support of big data technology and machine learning and face recognition. By combining bibliometrics with a systematic review, we aim to analyze the research foci and future development direction deeply, providing scholars with a comprehensive view of the field.
اظهر المزيد [+] اقل [-]Dunite carbonation in batch-tubular reactor النص الكامل
2020
Agrawal, Amit Kumar | Mehra, Anurag
For geological carbon sequestration, the reaction of aqueous CO₂ with silicate rock permits carbonate formation, achieving permanent carbon sequestration. The fractures available in silicate rock provide significant surface area for the precipitation of carbonates. The experiments were performed in a batch tubular reactor under diffusion-limited condition, with a special arrangement of a narrow tube filled with a 2800 g/L dunite slurry. The tube was kept open from the top, standing vertically filled with a CO₂-rich bulk solution under 1 barg CO₂ and temperatures ranging from 25 to 75 ᵒC for 7–30 days. After 7 days of the experiment, magnesite precipitation was seen inside the tube and the precipitation was continued for up to 30 days. The magnesite precipitation was identified by micro-Raman spectroscopy, X-ray diffraction, and scanning electron microscopy. Additionally, SiO₂ formation was seen in relative close vicinity to the magnesite precipitation. The precipitation on the surface of silicate rock might cover the fractures and pore spaces available, which may over time reduce the dissolution rate of dunite. Graphical Abstract
اظهر المزيد [+] اقل [-]Transcriptome analysis revealed cadmium accumulation mechanisms in hyperaccumulator Siegesbeckia orientalis L النص الكامل
2020
Xu, Xiaoxun | Zhang, Shirong | Cheng, Zhang | Li, Ting | Jia, Yongxia | Wang, Guiyin | Yang, Zhanbiao | Xian, Junren | Yang, Yuanxiang | Zhou, Wei
Siegesbeckia orientalis L. was identified as a novel Cd-hyperaccumulator and valuable phytoremediation material. However, the molecular mechanisms underlying Cd accumulation in S. orientalis are largely unknown. In this study, RNA-Seq analysis was performed to study the Cd-accumulating mechanisms in its roots with or without Cd treatment. The RNA-seq analysis generated 312 million pairs of clean reads and 78G sequencing data. De novo transcriptome assembly produced 355,070 transcripts with an average length of 823.59 bp and 194,207 unigenes with an average length of 605.68 bp. Comparative transcriptome analyses identified a large number of differentially expressed genes in roots under Cd stress, and functional annotation suggested that S. orientalis utilizes various biological pathways involving many gene networks working simultaneously to cope with the stress. This study revealed that four biological pathways were mainly involved in S. orientalis tolerance to Cd stress, including reactive oxygen species scavenging, phenylpropanoid biosynthesis pathway, Cd absorption and transport, and ABA signaling pathway. The genes related to photosynthesis and heavy metal transport are likely the potential candidates and could be further investigated to determine their roles in Cd tolerance in S. orientalis roots. These findings will be useful to understand the Cd accumulation mechanisms in S. orientalis and facilitate the study of phytoremediation at the molecular level in plants.
اظهر المزيد [+] اقل [-]