Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these ...beneficial outcomes requires an understanding of the relationships among biochar’s structure, stability, and contribution to soil fertility. Using quantitative 13C nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of ∼6 fused aromatic rings substituted by COO– groups that significantly increase the soils’ cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S. (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought (∼40–50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertility-enhancing form of soil organic matter.
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IJS, KILJ, NUK, PNG, UL, UM
The photochemical reduction of Cr(VI) by four low-molecular-weight organic acids (tartaric acid, citric acid, malic acid, and
n-butyric acid) in the presence of either dissolved Fe(III) in dilute ...aqueous solution or adsorbed Fe(III) on clay mineral surfaces (kaolinite, montmorillonite and illite) was investigated using batch reactors at a pH range from 3.5 to 4.5 at 25
°C. The results indicate that Fe(III) photocatalytic reduction of Cr(VI) by organic acids with α-OH is extremely fast. During a reaction period when less than 80% initial Cr(VI) was consumed, the reaction can be described as pseudo-first-order with respect to Cr(VI) when organic acid in excess. By plotting lnCr(VI) as a function of reaction time, rate constants of Cr(VI) reduction by organic acids are obtained. The rate constants involving the four acids are in the order: tartaric acid (with 2 carboxylic groups and 2 α-OH groups)
>
citric acid (with 3 carboxylic groups and 1 α-OH group)
≈
malic acid (with 2 carboxylic groups and 1 α-OH group)
≫
n-butyric acid (with 1 carboxylic group and no α-OH group). This order suggests that the number of α-OH but not the number of carboxylic groups is an important determinant of kinetics. With light, the reduction of Cr(VI) by citric acid is accelerated by clay minerals. The enhancement of Cr(VI) reduction is attributed to the catalysis of Fe(III) adsorbed on clay mineral surfaces. However, such an acceleration is markedly suppressed by introducing NaF into the reaction system since NaF forms a complex with Fe(III). It is concluded that the complex formation between Fe(III) and organic acid is a key step for the photocatalytic reduction of Cr(VI) in the presence of Fe(III) and organic acids with α-OH.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Frequent dusty weather has led to an increasing interest in dust aerosols, which were observed by lidar as nonspherical particles. To solve the problem of large errors in the previous inversion ...results of nonspherical aerosol particle size distribution (APSD), an inversion model of nonspherical APSD is proposed in this article. This inversion model is made up of three steps. First, the discrete dipole approximation (DDA) method was used instead of the Lorenz-Mie (Mie) theory to compute the optical properties of nonspherical particles. Second, the traditional generalized cross-validation (GCV) method was replaced by a hybrid algorithm and combined with Tikhonov's regularization. The hybrid algorithm combines a particle swarm optimization (PSO) with a genetic algorithm (GA). The problem of the instability of the Lagrange multiplier values is solved. Third, a multi wavelength polarization lidar and an aerodynamic particle sizer (APS) were used to detect dust aerosols in Yinchuan. The nonspherical property of the dust aerosol was verified by the depolarization ratio of the 532-nm polarization channel. Overall, the simulation shows that the hybrid algorithm gives more accurate results and that the real part of the complex refractive index has a greater effect on the nonspherical APSD than the imaginary part of the complex refractive index. There is a clear inverse relationship between the variation of dust aerosol quantities at high altitudes and near the ground. Calculations from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed the reason for this phenomenon. The model shows that dust aerosol number changes were influenced by updrafts from Russian and Afghan regions and Shaanxi.
Accumulating evidence suggests cancer cells exhibit a dependency on metabolic pathways regulated by nicotinamide adenine dinucleotide (NAD⁺). Nevertheless, how the regulation of this metabolic ...cofactor interfaces with signal transduction networks remains poorly understood in glioblastoma. Here, we report nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting step in NAD⁺ synthesis, is highly expressed in glioblastoma tumors and patient-derived glioblastoma stem-like cells (GSCs). High NAMPT expression in tumors correlates with decreased patient survival. Pharmacological and genetic inhibition of NAMPT decreased NAD⁺ levels and GSC self-renewal capacity, and NAMPT knockdown inhibited the in vivo tumorigenicity of GSCs. Regulatory network analysis of RNA sequencing data using GSCs treated with NAMPT inhibitor identified transcription factor E2F2 as the center of a transcriptional hub in the NAD⁺-dependent network. Accordingly, we demonstrate E2F2 is required for GSC selfrenewal. Downstream, E2F2 drives the transcription of members of the inhibitor of differentiation (ID) helix–loop–helix gene family. Finally, we find NAMPT mediates GSC radiation resistance. The identification of a NAMPT-E2F2-ID axis establishes a link between NAD+ metabolism and a self-renewal transcriptional program in glioblastoma, with therapeutic implications for this formidable cancer.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Glioblastoma stem cells (GSCs) are an important subpopulation in glioblastoma, implicated in tumor growth, tumor recurrence, and radiation resistance. Understanding the cellular mechanisms for chemo- ...and radiation resistance could lead to the development of new therapeutic strategies. Here, we demonstrate that CDC20 promotes resistance to chemotherapy and radiation therapy. CDC20 knockdown does not increase TMZ- and radiation-induced DNA damage, or alter DNA damage repair, but rather promotes cell death through accumulation of the pro-apoptotic protein, Bim. Our results identify a CDC20 signaling pathway that regulates chemo- and radiosensitivity in GSCs, with the potential for CDC20-targeted therapeutic strategies in the treatment of glioblastoma.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract A total of 10,339 positions of the five major Uranian satellites (Ariel, Umbriel, Titania, Oberon and Miranda) were collected at the Yunnan Observatories from 2013 to 2020 with the 1.0 m ...astrometric reflector. A median filtering method was applied to reduce the influence of the bright Uranus halo. All CCD observational data was analyzed by the newly developed CCD image-processing software with Gaia DR3 as the reference catalog. The impact of different exposure times on satellite positioning accuracy was evaluated. The observational positions of satellites were compared with theoretical positions from Institut de Mécanique Céleste et de Calcul des Éphémérides (DE441 and Lainey et al. 2015) and the mean offsets are from −0.″115 to 0.″103 in both R.A. and decl. for the five satellites. The standard deviation of the offsets are from 0.″008 to 0.″086 for the four greatest Uranian satellites and from 0.″037 to 0.″132 for Miranda in each direction. These precise observations of the five major Uranian satellites over an 8 yr period will be very useful for improving the orbital parameters of both Uranus and its five major satellites.
We report a compact all-fiber high-energy fiber laser that consists of a laser oscillator and a compression section. The laser oscillator generates the pulses with high energy and large chirp. The ...compression section is made of a piece of standard single-mode fiber that dechirps the chirped pulses. The compact all-fiber fiber laser produces pulses with 8 nJ of the pulse energy and 290 fs of the pulse duration.
Manganese oxides are considered to be main oxidants resulting in transformation of Cr(III) to Cr(VI) in soils. Oxidation of aqueous Cr(III), Cr(III)–EDTA and insoluble species of Cr(III), such as ...Cr(OH)
3, CrFe(OH)
6 and CrPO
4, by δ-MnO
2 was investigated in batch reaction systems at 25
°C and different pH values to predict the potential for Cr(III) oxidation in soil environments. Results indicate that Cr(III) can be rapidly oxidized to Cr(VI) at the beginning of the reaction; however, Mn(II) is produced and fills the adsorption sites on the manganese oxide surface. As a result, produced Mn(II) greatly slows Cr(III) oxidation by δ-MnO
2. Lower pH and higher concentration of manganese oxide markedly enhance the rate and extent of aqueous Cr(III) oxidation. The oxidation of Cr(III)–EDTA by manganese oxide is significantly affected by the chelating time between Cr(III) and EDTA and the molar ratio of EDTA to Cr(III). The formed complex ions of Cr(III)–EDTA are hardly oxidized by manganese oxide and no Cr(VI) was detected in a pH range of 5–6. The rate and extent of oxidation of Cr(OH)
3 and CrFe(OH)
6 by manganese oxide decrease with pH increasing from 2 to 4. No release of Cr(VI) was observed in the suspension of CrFe(OH)
6 and manganese oxide at pH 4 and in the suspension of CrPO
4 and manganese oxide at all pH levels tested. The results demonstrate that the order of stability of Cr(III) in these precipitates is CrPO
4
>
CrFe(OH)
6
>
Cr(OH)
3 in the presence of manganese oxide.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The accurate estimation of soil organic carbon (SOC) storage and determination of its pattern-controlling factors is critical to understanding the ecosystem carbon cycle and ensuring ecological ...security. The Sanjiang Plain, an important grain production base in China, is typical of ecosystems, yet its SOC storage and pattern has not been fully investigated because of insufficient soil investigation. In this study, 419 soil samples obtained in 2012 for each of the three soil depth ranges 0-30, 30-60, and 60-100 cm and a geostatistical method are used to estimate the total SOC storage and density (SOCD) of this region. The results give rise to 2.32 Pg C for the SOC storage and 21.20 kg m-2 for SOCD, which is higher than the mean value for the whole country. The SOCD shows notable changes in lateral and vertical distribution. In addition, vegetation, climate, and soil texture, as well as agricultural activities, are demonstrated to have remarkable impacts on the variation in SOCD of this region. Soil texture has stronger impacts on the distribution of SOCD than climate in the Sanjiang Plain. Specifically, clay content can explain the largest proportion of the SOC variations (21.2% in the top 30 cm) and is the most dominant environmental controlling factor. Additionally, the effects of both climate and soil texture on SOCD show a weakening with increasing soil layer depth. This study indicates that reducing the loss of SOC requires effective conservation and restoration efforts of wetlands and forestlands, as well as sensible fertilization. The results from this study provide the most up-to-date knowledge on the storage and pattern of SOC in the Sanjiang Plain and have important implications for the determination of ecosystem carbon budgets and understanding ecosystem services.
Aiming at fabrication of cellular metallic glasses with high mechanical properties, double edge notched samples were designed by orthogonal design method. Compressive tests on those samples were ...carried out to investigate mechanical responses induced by different notch settings. It was found that the notch tip distance and stress triaxiality are two key factors controlling yield strength and plasticity of notched samples. Besides, free volume theory factoring in hydrostatic stress was incorporated into finite element model to simulate shear band (SB) deformation process for different samples. Combined with experiments, simulations as well as microstructure observations, it was concluded that the notch tip distance effect could be ascribed by transition process between sparsely-intersected and densely-intersected SBs, and the later is the key to plasticity enhancement. Additionally, large stress triaxiality could improve the global plasticity by introducing densely-intersected SBs so as to hinder sample from fracturing along one major SB. The current work could offer useful data in providing direct evidence on fabrication of cellular materials as well as enriching shear band formation mechanism of monolithic metallic glasses.
•Notch tip distance and stress triaxiality are the key factors controlling the global yield strength and plasticity.•Constitutive model could reasonably describe shear banding process induced by different stress states.•Plasticity enhancement depends on the transition process between sparsely-intersected and densely-intersected SBs.•Current work could provide direct evidences for fabrication of cellular metallic glasses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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