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1.
Front Ecol Environ ; 17(7): 375-382, 2019 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-31875865

RESUMEN

Maintaining the continued flow of benefits from science, as well as societal support for science, requires sustained engagement between the research community and the general public. On the basis of data from an international survey of 1092 participants (634 established researchers and 458 students) in 55 countries and 315 research institutions, we found that institutional recognition of engagement activities is perceived to be undervalued relative to the societal benefit of those activities. Many researchers report that their institutions do not reward engagement activities despite institutions' mission statements promoting such engagement. Furthermore, institutions that actually measure engagement activities do so only to a limited extent. Most researchers are strongly motivated to engage with the public for selfless reasons, which suggests that incentives focused on monetary benefits or career progress may not align with researchers' values. If institutions encourage researchers' engagement activities in a more appropriate way - by moving beyond incentives - they might better achieve their institutional missions and bolster the crucial contributions of researchers to society.

3.
Heliyon ; 9(11): e22342, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-38074885

RESUMEN

The investigation of a proficient photocatalytic system for the degradation of organic pollutants holds significant importance in the field of environmental management. This study presents a binary type II heterojunction photocatalyst, Bi2MoO6/g-C3N4 which is synthesized using an eco-friendly ultrasonic-assisted method. Various characterization methods (XRD, FTIR, XPS, BET, TEM, UV-vis, and PL) are used to investigate the crystalline structures, composition, surface analysis, morphology, and optical properties of the photocatalyst. All the Bi2MoO6/g-C3N4 nanocomposites show better photocatalytic activity for Rhodamine B dye (Rh-B) degradation under Ultraviolet light irradiation than the pure g-C3N4. The photocatalytic activity of the 10 % Bi2MoO6/g-C3N4 nanocomposite is found to be the greatest among the tested samples. the 10 % Bi2MoO6/g-C3N4 nanocomposite demonstrates the ability to degrade 94.6 % of Rh-B (1 × 10-5 M) within 3 h, with a rate constant of 0.015 min-1. Notably, this rate constant is 7 times greater than that observed for pure g-C3N4, which has a rate constant of 0.00218 min-1. The effect of several reaction factors on the Rhodamine B (Rh-B) removal is studied. The enhanced photocatalytic activity of 10 % Bi2MoO6/g-C3N4 nanocomposite is mainly due to the formation of 2D/2D type II structures, increasing the active sites and the separation rate of photogenerated carriers. A possible photocatalytic reaction mechanism of Rhodamine B (Rh-B) degradation over Bi2MoO6/g-C3N4 is suggested based on active species trapping experiment. Moreover, the high stability and recyclability exhibited by the 10 % Bi2MoO6/g-C3N4 nanocomposite provide strong evidence supporting its suitability as a viable photocatalyst for wastewater treatment purposes.

4.
Sci Rep ; 13(1): 21879, 2023 Dec 11.
Artículo en Inglés | MEDLINE | ID: mdl-38072847

RESUMEN

The research focuses on utilizing gamma irradiation to synthesize polyacrylic acid-co-polyacrylamide p(AAm-co-AAc) hydrogels. The effect of synthetic parameters on physicochemical features of p(AAm-co-AAc) hydrogls were examined, including acrylic acid (AAc): acrylamide (AAm) weight ratios, monomer concentration, and gamma irradiation dosage (kGy). At the optimum synthetic conditions (30 kGy and 75% AAc), different chemical modifications are explored to incorporate sulfonate, hydroxyl, carboxyl, cysteine, thiol, and amine functional groups within the bare hydrogel (Cpd 0) structure. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses confirmed the success development of functionalized hydrogels (namely Cpd 1 to 6) with three-dimensional porous structures. These modified hydrogels include Cpd 1, a sulfonated hydrogel through a sulfonation reaction; Cpd 2, modified via NaOH hydrolysis; Cpd 3, modified using thionyl chloride; Cpd 4, incorporating cysteine modification through reaction with cysteine; Cpd 5, with 4-(Dimethylamino) benzaldehyde; and Cpd 6, modified with 3,4-Dimethylbenzoic acid.The effect of hydrogel composition and surface functionalities on the swelling capacity and interactions with scale-forming/heavy metal ions (e.g., Ba2+, Sr2+, and Cu2+) was investigated in saline water solution (NaCl = 1000 mg/L). Batch adsorption studies reveal that all modified hydrogels exhibited higher removal efficiency for the three metal ions than unmodified p(AAm-co-AAc) hydrogel, validating the key role of surface functionalities in tailoring hydrogel affinity for metal ions adsorption. Amongst these, NaOH-treated hydrogel (Cpd 2) outperformed all other modified ones in the removal of Cu2+, Ba2+, and Sr2+ ions, with maximum capacities of 13.67, 36.4, and 27.31 mg/g, respectively. Based on adsorption isotherm and kinetic modeling, the adsorption process of the three metal ions onto all modified hydrogels better obeyed Freundlich isotherm and pseudo-first-order kinetic models. Thermodynamic studies also indicated that the adsorption behavior of Sr2+ ions can exhibit both exothermic and endothermic characteristics, depending on the nature of hydrogel surface chemistry. Conversely, the adsorption process of Cu2+ and Ba2+ ions onto all modified hydrogels is endothermic, suggesting favorable chemical adsorption mechanisms. These findings reveal that the specific adsorption performance of hydrogel is dependent on the type of modification and the targeted heavy metal ions. Based on the nature of hydrogel surface functionality, surface modifications can change the charge density, hydrophilicity, and overall chemical environment of the hydrogel, offering a versatile approach to optimize the adsorption affinity/selectivity of hydrogel's in removing scale-forming/heavy metals from water solutions.

5.
ACS Omega ; 8(23): 20283-20292, 2023 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-37323399

RESUMEN

Aerogel is a high-performance thermal resistance material desired for high-temperature applications like dye-sensitized solar cells, batteries, and fuel cells. To increase the energy efficiency of batteries, an aerogel is required to reduce the energy loss arising from the exothermal reaction. This paper synthesized a different composition of inorganic-organic hybrid material by growing the silica aerogel inside a polyacrylamide (PAAm) hydrogel. The hybrid PaaS/silica aerogel was synthesized using different irradiation doses of gamma rays (10-60 kGy) and different solid contents of PAAm (6.25, 9.37, 12.5, and 30 wt %). Here, PAAm is used as an aerogel formation template and carbon precursor after the carbonization process at a temperature of (150, 350, and 1100 °C). The hybrid PAAm/silica aerogel was converted into aluminum/silicate aerogels after soaking in a solution of AlCl3. Then, the carbonization process takes place at a temperature of (150, 350, and 1100 °C) for 2 h to provide C/Al/Si aerogels with a density of around 0.18-0.040 gm/cm3 and porosity of 84-95%. The hybrid C/Al/Si aerogels presented interconnected networks of porous structures with different pore sizes depending on the carbon and PAAm contents. The sample with a solid content of 30% PAAm in the C/Al/Si aerogel was composed of interconnected fibrils whose diameter was about 50 µm. The structure after carbonization at 350 and 1100 °C was a condensed opening porous 3D network structure. This sample gives the optimum thermal resistance and a very low thermal conductivity of 0.073 (w/m·k) at low carbon content (2.71% at temperature 1100 °C) and high vpore (95%) compared with carbon content 42.38% and vpore (93%) which give 0.102 (w/m·k). This is because at 1100 °C, the carbon atoms evolve to leave an area between Al/Si aerogel particles, increasing the pore size. Furthermore, the Al/Si aerogel had excellent removal ability for various oil samples.

6.
Arch Environ Contam Toxicol ; 62(3): 361-8, 2012 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-21892762

RESUMEN

The distribution of natural nuclide gamma-ray activities and their respective annual effective dose rates, produced by potassium-40 (4°K), uranium-238 (²³8U), thorium-232 (²³²Th), and radium-226 (²²6Ra), were determined for 14 oilfield scale samples from the Middle East. Accumulated radioactive materials concentrate in tubing and surface equipment, and workers at equipment-cleaning facilities and naturally occurring radioactive materials (NORMs) disposal facilities are the population most at risk for exposure to NORM radiation. Gamma-spectra analysis indicated that photo-gamma lines represent the parents of 10 radioactive nuclides: ²³4Th, plutonium-239, actinium-228, ²²6Ra, lead-212 (²¹²Pb), ²¹4Pb, thallium-238 (²°8Tl), bismuth-212 (²¹²Bi), ²¹4Bi, and 4°K. These nuclides represent the daughters of the natural radioactive series ²³8U and ²³²Th with 4°K as well. The mean activity concentration of ²³8U, ²³²Th, and 4°K were found to be 25.8 ± 11.6, 18.3 ± 8.1, and 4487.2 ± 2.5% Bq kg⁻¹ (average values for 14 samples), respectively. The annual effective dose rates and the absorbed doses in air, both indoor and outdoor, for the samples were obtained as well. The results can be used to assess the respective hazard on workers in the field and represent a basis for revisiting current engineering practices.


Asunto(s)
Monitoreo de Radiación , Contaminantes Radiactivos/análisis , Humanos , Medio Oriente , Exposición Profesional/análisis , Exposición Profesional/estadística & datos numéricos , Radioisótopos de Potasio/análisis , Dosis de Radiación , Radio (Elemento)/análisis , Medición de Riesgo , Torio/análisis , Uranio/análisis
7.
Math Biosci Eng ; 19(12): 12500-12517, 2022 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-36654008

RESUMEN

Zagreb indices are well-known and historical indices that are very useful to calculate the properties of compounds. In the last few years, various kinds of Zagreb and Randic indices are investigated and defined to fulfil the demands of various engineering applications. Phenylenes are a class of conjugated hydrocarbons composed of a special arrangement of six- and four-membered rings. This special chain, produced by zeroth-order Markov process has been commonly appeared in the field of pharmacology and materials. Here, we compute the expected values of a multiplicative versions of the geometric arithmetic and atomic bond connectivity indices for these special hydrocarbons. Moreover, we make comparisons in the form of explicit formulae and numerical tables between the expected values of these indices in the random polyphenyl $ \mathbb{P}_n $ and spiro $ \mathbb{S}_n $ chains.


Asunto(s)
Hidrocarburos
8.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 7): m975-6, 2011 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-21836950

RESUMEN

In the binuclear centrosymmetric crystal structure of the title compound, [Cu(2)(C(7)H(14)N(5))(2)(C(9)H(21)P)(2)], all atoms except those of the isopropyl groups are approximately co-planar. The Cu(II) atom is in a distorted trigonal-planar CuN(2)P coordination. Bond angles around the amino N atom suggest sp(2) hybridization. Several intra-molecular C-H⋯N inter-actions are present involving tetra-zolate N atoms.

9.
Materials (Basel) ; 14(7)2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33916107

RESUMEN

Organic solar cells (OSCs), also known as organic photovoltaics (OPVs), are an emerging solar cell technology composed of carbon-based, organic molecules, which convert energy from the sun into electricity. Key for their performance is the microstructure of the light-absorbing organic bulk heterojunction. To study this, organic solar films composed of both fullerene C60 as electron acceptor and different mole percentages of di-[4-(N,N-di-p-tolyl-amino)-phenyl]-cyclohexane (TAPC) as electron donor were evaporated in vacuum in different mixing ratios (5, 50 and 95 mol%) on an ITO-coated glass substrate held at room temperature and at 110 °C. The microstructure of the C60: TAPC heterojunction was studied by grazing incidence wide angle X-ray scattering to understand the effect of substrate heating. By increasing the substrate temperature from ambient to 110 °C, it was found that no significant change was observed in the crystal size for the C60: TAPC concentrations investigated in this study. In addition to the variation done in the substrate temperature, the variation of the mole percent of the donor (TAPC) was studied to conclude the effect of both the substrate temperature and the donor concentration on the microstructure of the OSC films. Bragg peaks were attributed to C60 in the pure C60 sample and in the blend with low donor mole percentage (5%), but the C60 peaks became nondiscernible when the donor mole percentage was increased to 50% and above, showing that TAPC interrupted the formation of C60 crystals.

10.
Eur J Mass Spectrom (Chichester) ; 16(6): 679-92, 2010.
Artículo en Inglés | MEDLINE | ID: mdl-21173466

RESUMEN

Transition metals can have a significant impact in research related to the dosage optimization of superplasticizers. It is known that the presence of transition metals can influence such doses, and the application of a contemporary instrumental method to obtain the profiles of subsisting transition elements in concrete mixtures would be useful. In this work, inductively-coupled plasma mass spectrometry (ICP-MS) is investigated as a possible tool to track traces of transition metals in concrete mixtures. Depth profiling using ICP-MS on proofed and unproofed concrete shows the presence of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn at trace intensities in the bulk of the samples under investigation. The study demonstrates that the transition metals present in the concrete sample are largely a part of the cement composition and, to a minor degree, a result of exposure to the seawater after curing. The coated concrete samples have a metal distribution pattern similar to the uncoated samples, but slight differences in intensity bear testimony to the very low levels that originate from the exposure to seawater. While X-ray diffraction fails to detect these traces of metals, ICP-MS is successful in detecting ultra-trace intensities to parts per trillion. This method is not only a useful application to track traces of transition metals in concrete, but also provides information to estimate the pore size distribution in a given sample by very simple means.

11.
J Am Soc Mass Spectrom ; 22(8): 1403-8, 2011 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21953195

RESUMEN

Knowledge of trace metal 'grains' in asphaltenes could play a significant role in enhancing refining and processing of crudes and also in providing useful information on mechanistic and migratory features linked to asphaltenes. These metals originate directly from interaction of oils with source-rock, mineral matter, and formation water and their accumulation in asphaltene matrices could vary from oil well to oil well. Suitable asphaltene samples were subjected to high-performance ICP-MS laser depth profiling (213 nm) to depths of 50 µm at 5 µm intervals. The study was conducted in the absence of standardization and characteristic intensities originating from the metals of interest were measured. Ten metal profiles were investigated (Na, Mg, Al, Mn, Fe, Zn, Sr, Pb, V, and Ni). The experimental results showed non-uniform distribution of trace metals and identified areas where such metals agglomerate. The data suggested that certain chemical and physical conditions within the structure of asphaltenes are favorable for metal 'grain' formation at specific points. The exact mechanism for this behavior is not clear at this stage, and has considerable scope for future studies, including mathematical modeling simulations of asphaltenes. We also found that solid asphaltenes could be a useful forerunner of scale formation.

12.
Dalton Trans ; (40): 8746-54, 2009 Oct 28.
Artículo en Inglés | MEDLINE | ID: mdl-19809750

RESUMEN

Dioxomolybdenum(VI) complexes with the general formula [MoO2Cl2L2] (L2=3,3'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethyl-2,2'-bipyridine, 4,4'-dibromo-2,2'-bipyridine, 5,5'-dibromo-2,2'-bipyridine, 5,5'-diamino-2,2'-bipyridine; 5,5'-dinitro-2,2'-bipyridine; 5,5'-di-ethoxycarbonyl-2,2'-bipyridine; 6-phenyl-2,2'-bipyridine; 2,2':6',2''-terpyridine) have been prepared and characterised. [MoO2Cl2(5,5'-di-ethoxycarbonyl-2,2'-bipyridine)] has been examined by single crystal X-ray analysis. The complexes were applied as homogenous catalysts for the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as oxidising agent. The new compounds show an overall high activity and are highly selective catalysts in the epoxidation of cyclooctene. The stability of the complexes and differences in the catalytic activity can be clearly attributed to electronic contributions of the functional groups on bipyridine ligands and to steric restrictions. DFT calculations have assisted in a better understanding of the stability of the complexes and are in agreement with experiment. The influence of the terminal oxo ligands and the Lewis base ligands on the Mo center keep the compounds on quite a stable level of electron density.

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