Ca-Based Layered Double Hydroxides for Environmentally Sustainable Carbon Capture.

The process of carbon dioxide capture typically requires a large amount of energy for the separation of carbon dioxide from other gases, which has been a major barrier to the widespread deployment of carbon capture technologies. Innovation of carbon dioxide adsorbents is herein vital for the attainment of a sustainable carbon capture process. In this study, we investigated the electrified synthesis and rejuvenation of calcium-based layered double hydroxides (Ca-based LDHs) as solid adsorbents for CO2. We discovered that the particle morphology and phase purity of the LDHs, along with the presence of secondary phases, can be controlled by tuning the current density during electrodeposition on a porous carbon substrate. The change in phase composition during carbonation and calcination was investigated to unveil the effect of different intercalated anions on the surface basicity and thermal stability of Ca-based LDHs. By decoupling the adsorption of water and CO2, we showed that the adsorbed water largely promoted CO2 adsorption, most likely through a sequential dissolution and reaction pathway. A carbon capture capacity of 4.3 ± 0.5 mmol/g was measured at 30 °C and relative humidity of 40% using 10 vol % CO2 in nitrogen as the feed stream. After CO2 capture occurred, the thermal regeneration step was carried out by directly passing an electric current through the conductive carbon substrate, known as the Joule-heating effect. CO2 was found to start desorbing from the Ca-based LDHs at a temperature as low as 220 °C as opposed to the temperature above 700 °C required for calcium carbonate that forms as part of the Ca-looping capture process. Finally, we evaluated the cumulative energy demand and environmental impact of the LDH-based capture process using a life cycle assessment. We identified the most environmentally concerning step in the process and concluded that the postcombustion CO2 capture using LDH could be advantageous compared with existing technologies.

Underestimation of Sector-Wide Methane Emissions from United States Wastewater Treatment.

An increasing percentage of US waste methane (CH4) emissions come from wastewater treatment (10% in 1990 to 14% in 2019), although there are limited measurements across the sector, leading to large uncertainties in current inventories. We conducted the largest study of CH4 emissions from US wastewater treatment, measuring 63 plants with average daily flows ranging from 4.2 × 10-4 to 8.5 m3 s-1 (<0.1 to 193 MGD), totaling 2% of the 62.5 billion gallons treated, nationally. We employed Bayesian inference to quantify facility-integrated emission rates with a mobile laboratory approach (1165 cross-plume transects). The median plant-averaged emission rate was 1.1 g CH4 s-1 (0.1-21.6 g CH4 s-1; 10th/90th percentiles; mean 7.9 g CH4 s-1), and the median emission factor was 3.4 × 10-2 g CH4 (g influent 5 day biochemical oxygen demand; BOD5)-1 [0.6-9.9 × 10-2 g CH4 (g BOD5)-1; 10th/90th percentiles; mean 5.7 × 10-2 g CH4 (g BOD5)-1]. Using a Monte Carlo-based scaling of measured emission factors, emissions from US centrally treated domestic wastewater are 1.9 (95% CI: 1.5-2.4) times greater than the current US EPA inventory (bias of 5.4 MMT CO2-eq). With increasing urbanization and centralized treatment, efforts to identify and mitigate CH4 emissions are needed.

Methane Emissions from Municipal Wastewater Collection and Treatment Systems.

Municipal wastewater collection and treatment systems are critical infrastructures, and they are also identified as major sources of anthropogenic CH4 emissions that contribute to climate change. The actual CH4 emissions at the plant- or regional level vary greatly due to site-specific conditions as well as high seasonal and diurnal variations. Here, we conducted the first quantitative analysis of CH4 emissions from different types of sewers and water resource recovery facilities (WRRFs). We examined variations in CH4 emissions associated with methods applied in different monitoring campaigns, and identified main CH4 sources and sinks to facilitate carbon emission reduction efforts in the wastewater sector. We found plant-wide CH4 emissions vary by orders of magnitude, from 0.01 to 110 g CH4/m3 with high emissions associated with plants equipped with anaerobic digestion or stabilization ponds. Rising mains show higher dissolved CH4 concentrations than gravity sewers when transporting similar raw sewage under similar environmental conditions, but the latter dominates most collection systems around the world. Using the updated data sets, we estimated annual CH4 emission from the U.S. centralized, municipal wastewater treatment to be approximately 10.9 ± 7.0 MMT CO2-eq/year, which is about twice as the IPCC (2019) Tier 2 estimates (4.3-6.1 MMT CO2-eq/year). Given CH4 emission control will play a crucial role in achieving net zero carbon goals by the midcentury, more studies are needed to profile and mitigate CH4 emissions from the wastewater sector.

Environmental, human health, and economic implications of landfill leachate treatment for per- and polyfluoroalkyl substance removal.

Landfill leachate is commonly treated offsite with municipal wastewater. This offsite leachate treatment may be limited or no longer applicable due to the increasingly stringent regulations and concerns related to per- and polyfluoroalkyl substance (PFAS) discharge into the environment, resulting in development of full-scale, onsite leachate treatment facilities. To help landfills prepare for the potential shift from offsite to onsite leachate treatment for PFAS compliance, this study analyzed and compared the environmental, human health, and economic performances of a typical onsite and a typical offsite leachate treatment alternative through life cycle assessment (LCA) and life cycle cost assessment (LCCA) using a landfill site located in Zhuzhou, China as a testbed. Two distinct functional units (FUs) were investigated: 1 m3 of leachate treated and 1 g of PFAS removed. Our results show that the onsite scenario offered benefits from human health and economic perspectives, while the offsite scenario generally performed better from the environmental perspective when a leachate PFAS concentration of 150,704 ng/L was assumed. The extent of this tradeoff varied when different functional units were adopted. The onsite scenario will not be competitive from all three perspectives when PFAS concentration in the raw leachate is less than 1666 ng/L.

Managing dams for energy and fish tradeoffs: What does a win-win solution take?

Management activities to restore endangered fish species, such as dam removals, fishway installations, and periodic turbine shutdowns, usually decrease hydropower generation capacities at dams. Quantitative analysis of the tradeoffs between energy production and fish population recovery related to dam decision-making is still lacking. In this study, an integrated hydropower generation and age-structured fish population model was developed using a system dynamics modeling method to assess basin-scale energy-fish tradeoffs under eight dam management scenarios. This model ran across 150 years on a daily time step, applied to five hydroelectric dams located in the main stem of the Penobscot River, Maine. We used alewife (Alosa pseudoharengus) to be representative of the local diadromous fish populations to link projected hydropower production with theoretical influences on migratory fish populations on the model river system. Our results show that while the five dams can produce around 427 GWh/year of energy, without fishway installations they would contribute to a 90% reduction in the alewife spawner abundance. The effectiveness of fishway installations is largely influenced by the size of reopened habitat areas and the actual passage rate of the fishways. Homing to natal habitat has an insignificant effect on the growth of the simulated spawner abundance. Operating turbine shutdowns during alewives' peak downstream migration periods, in addition to other dam management strategies, can effectively increase the spawner abundance by 480-550% while also preserving 65% of the hydropower generation capacity. These data demonstrate that in a river system where active hydropower dams operate, a combination of dam management strategies at the basin scale can best balance the tradeoff between energy production and the potential for migratory fish population recovery.

Inhibition of the connexin 43 elevation may be involved in the neuroprotective activity of leptin against brain ischemic injury.

Leptin is a multifunctional hormone produced by the ob gene and is secreted by adipocytes that regulate food intake and energy metabolism. Numerous studies demonstrated that leptin is a novel neuroprotective effector, however, the mechanisms are largely unknown. Herein, we demonstrate the protective activities of leptin after ischemic stroke and provide the first evidence for the involvement of the connexin 43 (Cx43) in leptin-mediated neuroprotection. We found that leptin treatment reduces the infarct volume, improves animal behavioral parameters, and inhibits the elevation of Cx43 expression in vivo. In vitro, leptin reverses ischemia-induced SY5Y and U87 cells Cx43 elevation, secreted glutamate levels in medium and SY5Y cell death, these roles could be abolished by leptin receptor blocker. Additionally, leptin administration upregulated the extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation. Moreover, ERK1/2 inhibitors pretreatment reversed the effects of leptin on Cx43 expression, glutamate levels and cell apoptosis. In conclusion, the present study demonstrated that leptin can reduce the Cx43 expression and cell death both in vivo and in vitro via ERK1/2 signaling pathway. This result provides a novel regulatory signaling pathway of the neuroprotective effects of leptin and may contribute to ischemic brain injury prevention and therapy.

Is leptin a predictive factor in patients with lung cancer?

OBJECTIVES: The aim of this study was to evaluate the expression and clinical significance of leptin in lung cancer. METHODS: 126 patients with lung cancer ranged from 30 to 83years of age were studied. Serum leptin levels were determined by ELISA. The mRNA and protein levels of leptin in normal and lung cancer tissues were measured by RT-PCR and immunohistochemistry. The relationships between leptin levels and clinicopathological factors were evaluated by Wilcoxon rank sum or Kruskal-Wallis H test. RESULTS: Serum leptin levels in lung cancer patients were significantly higher compared to those in controls and leptin expression in lung cancer tissue was markedly increased than that in normal lung tissue (both P<0.050). CONCLUSIONS: Determination of leptin levels might provide useful predictive information for lung cancer.

Leptin attenuates lipopolysaccharide-induced apoptosis of thymocytes partially via down-regulation of cPLA2 and p38 MAPK activation.

Leptin, a 16-kDa protein that is mainly secreted by adipocytes, plays a protective role in many cell types. It has been shown that leptin acts in the central and peripheral immune system to protect thymocytes. Cytosolic phospholipase A(2) (cPLA(2)) is an enzyme that can specifically initiate the release of arachidonic acid (AA) to produce eicosanoids, which regulate inflammation and immune responses. Our previous work has shown that leptin is important to prevent apoptosis of thymocytes. However, the role of cPLA(2) is still unclear, and the precise mechanism also remains to be elucidated. In this work, we demonstrated that leptin inhibited the LPS-induced toxicity and apoptosis of thymocytes. Western blot and RT-PCR showed that leptin led to a reduction of cPLA(2) activity and mRNA level, as well as caspase-3 cleavage. Moreover, we found that leptin could decrease the activation of p38 MAPK. Accordingly, we pre-treated apoptotic thymocytes with the p38 MAPK inhibitor, SB203580 and observed an effect similar to the leptin alone treated group. SB203580 also suppressed expression of cPLA(2) and cleavage of caspase-3. Based on these results, we suggest that leptin could attenuate LPS-induced apoptotic injury in mouse thymocyte cells, mainly through the p38/cPLA(2) signalling pathway. The study of the regulatory role of leptin in LPS-induced thymocyte apoptosis can help to explain the role of leptin in the immune system and may provide a novel treatment option in cases of severe trauma, infection, shock, organ failure and autoimmune disease caused by thymic atrophy.

Leptin attenuates cerebral ischemia injury through the promotion of energy metabolism via the PI3K/Akt pathway.

The purpose of this study was to investigate the protective mechanism of leptin-mediated metabolic recovery against cerebral injury after ischemia and reperfusion. We determined the neurologic deficit score, extent of brain edema, and infarct volume after reperfusion. The histopathologic alterations and changes in glucose uptake in the brain were also observed. Moreover, the levels of lactate dehydrogenase (LDH), lactic acid, pyruvate, and ATP in brain tissue were detected. Leptin levels in serum were also detected. To further define leptin-induced neuroprotective signaling pathways, we examined the levels of phosphorylated Akt (p-Akt) in the brain and in cultured cells. After transient ischemia, leptin treatment markedly reduced the neurologic deficits, cerebral infarct volume, and brain edema. After leptin injection, ATP, leptin, and p-Akt levels were significantly increased, LDH levels and lactic acid/pyruvate ratio were noticeably reduced, and histopathologic injuries were alleviated, which were all reversed by the PI(3)K inhibitor LY294002. These data show that leptin ameliorates cerebral ischemia/reperfusion injury by enhancing p-Akt, which in turn improves the supply of energy. The PI(3)K/Akt pathway was found to be the critical pathway for the mediation of leptin-induced neuroprotection, a finding that may prove to be useful in the treatment of ischemic stroke.

Core-shell nanoarchitectures: a strategy to improve the efficiency of luminescence resonance energy transfer.

The development of core-shell nanoparticles has shown a wide range of new applications in the fields of chemistry, bioscience, and materials science because of their improved physical and chemical properties over their single-component counterparts. In the present work, we took the core-shell nanoarchitectures as an example to research the luminescence resonance energy transfer (LRET) process between a luminescent Tb3+ chelate, N,N,N(1),N(1)-[4'-phenyl-2,2':6',2'-terpyridine-6,6'-diyl]bis(methylenenitrilo)tetrakis(acetate)-Tb3+ (PTTA-Tb3+), and an organic dye, 5-carboxytetramethylrhodamine (CTMR). PTTA-Tb3+ and CTMR were chosen as the donor-acceptor pair of LRET in our model construction because of their effective spectral overlapping. The core-shell nanoparticles featuring a CTMR-SiO2 core surrounded by a concentric PTTA-Tb3+-SiO2 shell were prepared using a reverse microemulsion method. These nanoparticles are spherical, uniform in size, and highly photostable. The results of LRET experiments show that the sensitized emission lifetime of the acceptor in the nanoparticles is significantly prolonged (∼246 µs), which is attributed to the long emission lifetime of the Tb3+ chelate donor. According to the results of the steady-state and time-resolved luminescence spectroscopy, an energy transfer efficiency of ∼80% and a large Förster distance between the donor and the acceptor in the core-shell nanoparticles are calculated, respectively. The new core-shell nanoparticles with a high LRET efficiency and long Förster distance enable them to be promising optical probes for a variety of possible applications such as molecular imaging and multiplex signaling.

A lanthanide-complex-based ratiometric luminescent probe specific for peroxynitrite.

A lanthanide-complex-based ratiometric luminescence probe specific for peroxynitrite (ONOO(-)), 4'-(2,4-dimethoxyphenyl)-2,2':6',2''-terpyridine-6,6''-diyl]bis(methylenenitrilo)tetrakis(acetate)-Eu(3+)/Tb(3+) ([Eu(3+)/Tb(3+)(DTTA)]), has been designed and synthesized. Both [Eu(3+)(DTTA)] and [Tb(3+)(DTTA)] are highly water soluble with large stability constants at approximately 10(20), and strongly luminescent with luminescence quantum yields of 10.0 and 9.9%, respectively, and long luminescence lifetimes of 1.38 and 0.26 ms, respectively. It was found that the luminescence of [Tb(3+)(DTTA)] could be quenched by ONOO(-) rapidly and specifically in aqueous buffers, while that of [Eu(3+)(DTTA)] did not respond to the addition of ONOO(-). Thus, by simply mixing [Eu(3+)(DTTA)] and [Tb(3+)(DTTA)] in an aqueous buffer, a ratiometric luminescence probe specific for time-gated luminescence detection of ONOO(-) was obtained. The performance of [Tb(3+)(DTTA)] and [Eu(3+)/Tb(3+)(DTTA)] as the probes for luminescence imaging detection of ONOO(-) in living cells was investigated. The results demonstrated the efficacy and advantages of the new ratiometric luminescence probe for highly sensitive luminescence bioimaging application.

Preparation and time-gated luminescence bioimaging application of ruthenium complex covalently bound silica nanoparticles.

Luminescent ruthenium(II) complex covalently bound silica nanoparticles have been prepared and used as a probe for time-gated luminescence bioimaging. The new nanoparticles were prepared by copolymerization of a luminescent Ru(II) complex tris(5-amino-1,10-phenanthroline)ruthenium(II) conjugated with 3-aminopropyl(triethoxy)silane (APS-Ru conjugate), free (3-aminopropyl)triethoxysilane (APS) and tetraethyl orthosilicate (TEOS) in a water-in-oil reverse microemulsion consisting of Triton X-100, n-octanol, cyclohexane and water in the presence of aqueous ammonia. Characterization by transmission electron microscopy indicates that the nanoparticles are monodisperse, spherical and uniform in size, 64+/-4 nm in diameter. Compared with the dye-doping nanoparticles, dye leakage of the new nanoparticles was remarkably decreased. In addition, it was found that the Ru(II) complex luminescence could be effectively enhanced with a longer luminescence lifetime (approximately 2.3 micros) after forming the nanoparticles, which enables the nanoparticles to be suitable as a bioprobe for time-gated luminescence bioimaging applications. The nanoparticle-labeled streptavidin was prepared and successfully used for time-gated luminescence imaging detection of an environmental pathogen, Giardia lamblia, with high specificity and sensitivity.

[Fluorescence spectra and quantum yield of TiO2 nanocrystals synthesized by alcohothermal method].

Fluorescence spectra and fluorescence quantum yield of TiO2 nanocrystals were studied. Using tetra n-butyl titanate as a starting material, a facile alcohothermal technique was used to synthesize TiO2 nanocrystals. As can be seen from the transmittance electron microscopy (TEM) image, TiO2 nanocrystals with a relatively uniform particle size distribution of < 10 nm are present in the transparent sol. The transparent sol presents a strong stable fluorescence emission with a maximum at 450 nm, which is greatly dependent on the size quantization effects, defect energy level and the surface state of TiO2 nanocrystals. The quantum yield (gamma) of TiO2 was determined by the relative comparison procedure, using freshly prepared analytical purity quinine sulfate in 0.05 mol x L(-1) H2SO4 as a relative quantum yield standard. The emission quantum yield of TiO2 nanocrystals prepared in alcoholic media was calculated to be about 0.20 at wavelengths ranging from 330 to 370 nm, which was much higher than the values reported in previous works. So, it is supposed that nano-TiO2 will be applied as a potential quantum dots fluorescence probe in biological analysis.

High photoluminescence quantum yield of TiO2 nanocrystals prepared using an alcohothermal method.

Highly dispersible TiO2 nanocrystals (approximately 6 nm) were prepared by an alcohothermal method. A strong and stable photoluminescence emission with a maximum at 450 nm was observed in the original TiO2 nanocrystals colloid. Compared with the emission from quinine sulphate in 0.05 mol/L sulphuric acid, the emission quantum yield of TiO2 nanocrystals was determined to be about 0.20, which was much higher than the values (0.002 and 0.001) reported in previous studies. The fluorescence micrograph of TiO2 nanocrystals encapsulated in lipsomes shows that TiO2 nanocrystals prepared in such a way have potential application as a fluorescence probe in biological imaging. Research on the luminescence mechanism indicates that the surface state and extent of crystallization of the TiO2 nanocrystals are crucial factors in the high photoluminescence quantum yield obtained in this study.