764,728 research outputs found
Structural and electrochemical characterization of xLi[Li1/3Mn2/3]O2·(1 - x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) as cathode materials for lithium ion batteries
No full textA series of cathode materials with molecular notation of xLi[Li1/3Mn2/3]O2·(1 - x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li1/3Mn2/3]O2·0.4Li[Ni1/3Mn1/3Co1/3]O2 (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g-1 between 2.0 and 4.8 V at 18 mA g-1. © 2008 Elsevier B.V. All rights reserved
A new bound for the smallest x with ?(x) > li(x)
No full textWe reduce the leading term in Lehman's theorem. This improved estimate allows us to refine the main theorem of Bays and Hudson [2]. Entering 2,000,000 Riemann zeros, we prove that there exists x in the interval [exp (727.951858), exp (727.952178)] for which ?(x) - li(x) > 3.2 × 10151. There are at least 10154 successive integers x in this interval for which ?(x) > li(x). This interval is strictly a sub-interval of the interval in Bays and Hudson, and is narrower by a factor of about 12
Chemical Lake Restoration Methods: From Alum to Innovative Composite Materials
No full textThis chapter evaluated a spectrum of chemical restoration approaches
of eutrophic water systems, highlighting the key role of internal nutrient loads to
guide remediation methods that control eutrophication. The usage of P- and joint
P-/N-inactivation agents have been considered as feasible restoration tools through
capacity and application methods in alignment with a wide spectrum of individuallyexamined nature-contexts, including that of water quality, algal blooms, flora, and
fauna. Moreover, an integrated approach was developed to evaluate those restoration
tools of degraded waters through specified conditions when P-inactivation agent was
applied
Novel Composite Materials as P-Adsorption Agents and Their Potential Applications as Fertilizers
No full textIn a world with high demand in P for the maintenance of soil fertility and
crop productivity, this chapter introduced the types and sources of P fertilizers in
soil. Specifically chemical fertilizers were discussed, with phosphate rock being the
primary source of phosphate, versus organic phosphate fertilizers, such as P humates
and organominerals. Moreover, novel composite materials that have been used as
P-adsorption agents are proposed as an alternative source of soil P fertilizers, which
could be effective soil conditioners, slowly releasing macro- and micro-nutrients in
agricultural soils
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Investigation of Ti/Au Transition-Edge Sensors for Single-Photon Detection
No full textTransition-edge sensors (TES) are remarkable superconducting devices for a wide range of radiation detection with the ability of both energy resolution and counting photons. For the detection of single photons at telecom wavelength, optical Ti/Au bilayer TESs are fabricated and characterized. The superconducting transition temperature (T-c) of the Ti/Au films is effectively tuned from 162 to 72 mK by increasing the relative thickness ratio between the Au and Ti layer. The sensitive area is 20 mu m x 20 mu m, on which an SiO2/SiNx antireflection structure is coated by an ICP-PECVD process. The TES device shows an energy resolution of 0.19 eV and can discriminate up to 36 incident photons, with an effective time constant around 107 mu s at 95 mK
Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49
No full textThe existence of black holes of masses similar to 10(2)-10(5)M(circle dot) has important implications for the formation and evolution of star clusters and supermassive black holes. One of the strongest candidates to date is the hyperluminous X-ray source (HLX1), possibly located in the S0- a galaxy ESO 243-49, but the lack of an identifiable optical counterpart had hampered its interpretation. Using the Magellan telescope, we have discovered an unresolved optical source with R = 23.80 +/- 0.25 mag and V = 24.5 +/- 0.3 mag within HLX1's positional error circle. This implies an average X-ray/optical flux ratio similar to 500. Taking the same distance as ESO 243-49, we obtain an intrinsic brightness M-R = -11.0 +/- 0.3 mag, comparable to that of a massive globular cluster. Alternatively, the optical source is consistent with a main-sequence M star in the Galactic halo (for example an M4.4 star at approximate to 2.5 kpc). We also examined the properties of ESO 243-49 by combining Swift/Ultraviolet/Optical Telescope (UVOT) observations with stellar population modelling. We found that the overall emission is dominated by a similar to 5-Gyr-old stellar population, but the UV emission at approximate to 2000 angstrom is mostly due to ongoing star formation at a rate of similar to 0.03M(circle dot) yr(-1). The UV emission is more intense (at least a 9 sigma enhancement above the mean) north-east of the nucleus, in the same quadrant as HLX1. With the combined optical and X-ray measurements, we put constraints on the nature of HLX1. We rule out a foreground star and a background AGN. Two alternative scenarios are still viable. HLX1 could be an accreting intermediate mass black hole in a star cluster, which may itself be the stripped nucleus of a dwarf galaxy that passed through ESO 243-49, an event which might have caused the current episode of star formation. Or, it could be a neutron star in the Galactic halo, accreting from an M4-M5 donor star
New performing GC columns with unmatched separation capabilities
No full textGas chromatography (GC) is widely used for qualitative and quantitative analysis in numerous fields, such as petroleum, chemical industry, agriculture, environmental protection, medicine, and so on, due to its high
versatility, high selectivity, simplicity of use, analysis speed, and low sample consumption. The column is the heart of a GC instrumentation, which allows the analyte separation and their recognition and quantification. Commercial columns do not always allow a complete peak separation when compounds (i.e., isomers) are very
similar in molecular weight, polarity, and vapor pressure. The choice of the correct stationary phase, with high selectivity towards target analytes, is the key to obtaining the required chromatographic separation and the subsequent qualitative and quantitative analysis.
Considering the rapid polymer science development and the growing demand for new columns with
improved resolution capabilities, in this work novel stationary phases for capillary GC have been designed, synthesized, and characterized in terms of polarity range, resolution, column efficiency, thermal stability, filmforming properties, and support-deactivating capacity1-5. The separation features of these novel stationary phases allow high-resolution performances for a wide range of compounds, like aromatic anilines, xylenes, aromatic amines, halogenated benzenes, and aromatic aldehydes, with marked capabilities toward isomer separations.References:
[1] T. Sun, M. Ba, Y. Song, W. Li, Y. Zhang, Z. Cai, S. Hu, X. Liu, D. Nardiello, M. Quinto, Analytica Chimica Acta, 2024, 1291, art. no. 342221.
[2] T. Sun, R. Chen, Q. Huang, M. Ba, Z. Cai, H. Chen, Y. Qi, H. Chen, X. Liu, D. Nardiello, M. Quinto, Analytica
Chimica Acta, 2023, 1251, art. no. 340979.
[3] T. Sun, R. Chen, Q. Huang, M. Ba, Z. Cai, S. Hu, X. Liu, D. Nardiello, M. Quinto, ACS Applied Materials and Interfaces, 2022, 14 50, pp. 56132-56142
[4] R. Chen, Z. Cai, W. Li, Q. Huang, D. Nardiello, M. Quinto, X. Liu, S. Hu, T. Sun, Chemistry and Biodiversity, 2022,
19, art. no. e202200829
[5] Q. Huang, Z. Cai, R. Chen, W. Zhang, D. Nardiello, M. Quinto, X. Liu, S. Hu, T. Sun, Microchemical Journal, 2022,
183, art. no. 10808
Investigation on temperature dependence of photoluminescence in Sr(1.7)Eu(0.3)M(x)CeO(4.15+x/2) (M = Li(+), Na(+), K(+), x=0, 0.3) red phosphors
No full textThe temperature-dependent luminescence of Sr(1.7)Eu(0.3)M(x)CeO(4.15+x/2) (M=Li(+), Na(+), K(+), x=0, 0.3) samples was investigated and discussed in the temperature range from 303 to 573 K. It is found that the thermal quenching temperature of samples decreases with Li(+)-/Na(+)-doping but increases with the incorporation of K(+). We suggest that these observations are resulted from two factors. One is that the incorporation of Li(+)/Na(+)/K(+) ions reduces the strength of potential field at the O(2-) sites, and then results in a red-shift of the Eu-O charge transferband. The other is that Delta r expands with Li(+)-/Na(+)-doping but shrinks with K(+)-doping. We consider that it is a feasible way to adjust the temperature-dependent luminescence properties of materials by introducing appropriate impurities. (C) 2010 Elsevier B.V. All rights reserved
Algorithm for sea surface wind retrieval from TerraSAR-X and TanDEM-X data
No full textA Geophysical Model Function (GMF), denoted XMOD2, is developed to retrieve sea surface wind field from Xband
TerraSAR-X/TanDEM-X (TS-X/TD-X) data. In contrast to
the previously developed XMOD1, XMOD2 consists of a
nonlinear GMF, and thus, it depicts the difference between
upwind and downwind of the sea surface backscatter in X-band SAR imagery. By exploiting 371 collocations with in situ buoy measurements which are used as the tuning dataset together with analysis wind model results, the retrieved TS-X/TD-X sea surface wind speed using XMOD2 shows a close agreement with buoy measurements with a bias of -0.32 m/s, an RMSE of 1.44 m/s and a scatter index (SI) of 16.0%. Further validation using an independent dataset of 52 cases shows a bias of -0.17 m/s, an RMSE of 1.48 m/s, and SI of 17.0% comparing with buoy measurements. To apply XMOD2 to TS-X/TD-X data acquired at HH polarisation, we validate three X-band SAR Polarisation Ratio (PR) models that were tuned using TS-X dual polarisation data by comparing the retrieved sea surface wind speed with buoy measurements
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