Search

The study investigates the effect of emissions of particulate matter arising out of different construction activities from five construction sites in Kanpur city, India. Limited research studies on exposure assessments related to particulate matter (PM) emissions from construction activities in the Indian context contribute to the uniqueness of this study. It was observed that for all study areas the concentrations of particulate matter (PM2.5 and PM10) exceeded the National Ambient Air Quality Standard (NAAQS) by a factor of 18–20. The highest concentration of PM10 (1308; 1267 µg/m3) and PM2.5 (1056; 1123 µg/m3) was associated with construction activity related to cutting and laying of tiles observed over the two monitoring campaigns conducted during November–December 2019 and January–February 2020. The human health risk exposure assessment assessed on relative risk (RR) determined on WHO methodology showed that the highest RR values of 2.669 and 4.13 were obtained for emissions of PM10 and PM2.5, respectively, from laying and cutting of tiles. The attributable factor (AF) from both PM10 (AF = 0.6253) and PM2.5 (AF = 0.757) also showed higher possibility of respiratory diseases for workers associated with laying and cutting of tiles. Health impact assessment conducted using the International Council for Radiological Protection (ICRP) model also confirmed that maximum and minimum deposition rates of particulates occurred for construction activities associated with cutting and laying of tiles and painting and washing, respectively. This suggests potential occupational health hazards for workers involved in construction activities being exposed to high levels of PM concentrations. [ABSTRACT FROM AUTHOR]

Thermophysical properties of aqueous pluronic solutions of P85 and P85–P123 systems with concentrations varying between 0.1 and 11 mass% for P85 and equimolar solution of 11 mass% P85-10 mass% P123 were measured in the absence and presence of solubilized lavender oil at temperatures below and above their critical micellization temperature in the temperature range of 288.15 K to 323.15 K. Maximum oil solubility was 3% (v/v) in the case of 11 mass% P85 and 2% (v/v) for mixed P85–P123 system. From density and sound speed measurements thermodynamic parameters like apparent molar volume, isentropic compressibility and expansibility were derived to evaluate the interactions of these block copolymers below and above the micellar region in pure and mixed micellar states. Apparent molar isentropic compressibility exhibited unusual variation with concentration which could be explained in light of pre-micellar aggregate formation. Isothermal titration calorimetry (ITC) was used to evaluate the energy changes involved in the aggregation processes for these systems. Critical micelle concentration (cmc) for P85 was found to be 0.74 mass% and pre-micellar aggregation was observed at 0.276 mass% from ITC study. Enthalpy of pre-micellar aggregation and micellization for oil-solubilized P85 solution were found to be 60 kJ mol−1 and 15 kJ mol−1 in the absence of oil. Micellization enthalpy for P85–P123 system was obtained as 72 kJ mol−1 and 142 kJ mol−1, respectively, in the absence and presence of solubilized oil. No pre-micellar aggregation was observed in mixed micelle system. DLS study was carried out to corroborate the findings obtained from densimetry and calorimetry. [ABSTRACT FROM AUTHOR]

Studies are conducted on an Al-6061 alloy reinforced with in situ ceramic mixture (AlO-SiC-C). The mixture is prepared by carbothermal reduction of flyash in a plasma reactor, where SiO is converted to SiC. The strength values for Al-6061-flyash (FA) and Al-6061-plasma synthesized flyash (PSFA) composites are 35% and 63% higher than that of the Al-6061 alloy. Wear resistance of the developed alloy composite prepared with treated flyash (Al-6061-PSFA) has increased two-fold in comparison to virgin alloy (Al-6061) and 1.5 fold higher in comparison to a similar alloy composites prepared with untreated flyash (Al-6061-FA). The unique property of the developed alloy composite is due to harder SiC particle reinforcement. Excess carbon in the form of graphite and the unique morphological feature of microstructure have enhanced the properties such as strength and wear resistance of the developed alloy composite. [ABSTRACT FROM AUTHOR]

The present investigation develops a next-generation hybrid Al metal matrix composite using coconut shell ash (CSA) and graphite (Gr) reinforcement. Stir-casting is adapted to prepare an Al-1100-based composite. Three other composites of Al-AlO, Al-AlO-Gr, and Al-CSA are prepared that contain equivalent volume fractions of AlO, CSA, and Gr. These assist in comparisons among the three composites and the developed hybrid Al-CSA-Gr composite. The study reveals that the addition of 3 pct Gr improves the specific strength, toughness, and tribological properties. The Al-CSA composite shows better mechanical properties, such as tensile strength and hardness, than the other three composites. Gr addition helps the hybrid Al-CSA-Gr composite to attain better tribological properties with a slightly lower specific strength. Scanning electron microscopy studies of the worn material surfaces corroborate the findings of the abrasion testing. Elemental analyses by energy-dispersive X-ray spectroscopy of the debris from the counter-face of the tribo surface confirm the presence of Al, O, Si, Fe, Mn, and C. [ABSTRACT FROM AUTHOR]

In the present investigation a new ternary ceramic matrix composite is developed from Indian fly ash by thermal treatment under reducing atmosphere. The ternary mixture, comprising of AlO-SiC-C, is formed by insitu conversion of SiO to SiC in the fly ash under reducing atmosphere. Analyses of the treated product by XRD, SEM, and EDAX have ensured formation of SiC from SiO. Converted SiC are rod shaped whiskers with the aspect ratio ranging between 40 to 50. The ternary mixture is added to aluminum melt in a bottom pouring pit type resistance furnace for the preparation of novel aluminum fly ash metal matrix composite (ALFMMC). Physical and mechanical properties of the novel ALFMMC (treated fly ash) composite are evaluated. For comparison purpose, aluminum fly ash composite is prepared with (untreated flyash) under identical condition of melting and casting. Wear resistance is found to be superior for the novel composite. [ABSTRACT FROM AUTHOR]

A novel method is adapted to prepare an in situ ceramic composite from waste colliery shale (CS) material. Heat treatment of the shale material, in a plasma reactor and/or in a high temperature furnace at 1673 K (1400 °C) under high vacuum (10 Torr), has enabled in situ conversion of SiO to SiC in the vicinity of carbon and AlO present in the shale material. The composite has the chemical constituents, SiC-AlO-C, as established by XRD/EDX analysis. Particle sizes of the composite range between 50 nm and 200 μm. The shape of the particles vary, presumably rod to spherical shape, distributed preferably in the region of grain boundaries. The CS composite so produced is added to aluminum melt to produce Al-CS composite (12 vol. pct). For comparison of properties, the aluminum metal matrix composite (AMCs) is made with AlO particulates (15 vol. pct) with size <200 μm. The heat-treated Al-CS composite has shown better mechanical properties compared to the Al-AlO composite. The ductility and toughness of the Al-CS composite are greater than that of the Al-AlO composite. Fractographs revealed fine sheared dimples in the Al-CS composite, whereas the same of the Al-AlO composite showed an appearance of cleavage-type facets. Abrasion and frictional behavior of both the composites have been compared. The findings lead to the conclusion that the in situ composite developed from the colliery shale waste material has a good future for its use in AMCs. [ABSTRACT FROM AUTHOR]

Al-AlO (18%) composite was prepared by stir-cast melt technique. The microstructures showed uniform distribution of particulates, dispersed in the matrix. There exists discontinuity (~0.25 μm) in the interface between particulates and matrix. The composite was hot forged. Hot working resulted in fine recrystallized microstructure with particulates dispersed along grain boundaries. Formation of pancake microstructure with some inhomogeneity in the microstructure along three faces of the forged composite was observed. The discontinuity across the interface between Al-AlO was reduced to 0.125 μm after forging. The as-cast and forged Al-AlO composites showed higher wear resistance than pure Al. In lubricant media, there was no significant wear observed for either the as-cast or forged composite, whereas Al had shown higher wear at 50 N load. [ABSTRACT FROM AUTHOR]

The structural characteristics of La1.85Sr0.15Cu1− xZn xO4 have been investigated over a wide composition range, viz. for x = 0.0, 0.1, 0.2, and 0.4, using powder neutron diffraction. The strong influence of substitution of the nonmagnetic Zn, which destroys superconductivity in the parent phase for rather low dopant concentration x ≲ 0.1, and the change of symmetry from the tetragonal to orthorhombic structure for x ≤ 0.2, are discussed. [ABSTRACT FROM AUTHOR]

Lactogenesis in mammary gland of the mouse requires cortisol (or corticosterone) and prolactin. In this paper we review some recent findings in our laboratory regarding influence of the corticosteroid on casein mRNA activity of lactating mammary gland. Adrenal ablation in nursing mothers results in loss of larger ribosomal aggregates (polysomes) from mammary cells; and this is accompanied by virtual abolition of immunologically detectable casein synthesis activity of the polysomes. Immunologically determined casein mRNA activity in phenol-chloroform-extracted lactating mammary cell RNA was assayed in ascites tumor cell ribosome cell-free protein synthesis system. Adrenalectomy induces 90% loss of casein mRNA activity of mammary cells of nursing mothers; this adverse response is also preventable by cortisol therapy of the animal. This suggests that the glucocorticoid influences the concentration of functionally active casein mRNA in the mammary cells. Cortisol treatment of adrenalectomized mothers also causes a pronounced increase of precursor ([H]uridine) incorporation into both rRNA and poly(A) mRNA. The latter includes mRNA species having a sedimentation value lower than 18S rRNA. Isolated nuclei of lactating mammary cells were assayed in an in vitro RNA polymerase system. RNA synthesized by the isolated nuclei in vitro after analysis on Sigmacell revealed that it includes poly(A) mRNA. This finding improves the feasibility of monitoring the influence of the glucocorticoid on mRNA transcriptional activity by the mammary chromatin. In addition results are presented to show that casein mRNA is inducible in the mammary cells in organ culture of the whole mammary gland in medium containing insulin, prolactin and cortisol. The significance of these findings concerning elucidation of the molecular mechanisms of synergism between the glucocorticoid and prolactin on modulation of the milk protein mRNA, and hence the developmental biology of the mammary gland, is discussed. [ABSTRACT FROM AUTHOR]

The effect of various parameters, namely amount of prestrain, time of aging, and temperature of aging on the response, that is the increase in the yield strength, of a dual-phase steel was studied by applying statistical design of experiments. A regression equation was developed between the response and the parameters. The equation was corrected by Student 't' test and was found to be adequate as checked by Fisher 'F' test and random experiment. Within the range of variables studied, the amount of prestrain, the time of aging, and the temperature of aging had negative, insignificant, and very significantly positive influence, respectively. An attempt was made to achieve a maximum for the response surface. The maximum was found to result from a combination of the parameters such as 0.5% tensile prestrain, aging time of 12 min, and aging temperature of 320°C. [ABSTRACT FROM AUTHOR]

The effect of Ca doping in EuBaSrCu3O7−δ has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measurements. X-Ray diffraction analyses of the samples showed that up to 30 at.% Ca can be substituted for Sr in EuBaSrCu3O7−δ, which has orthorhombic symmetry. The orthorhombicity decreases with increase in x in EuBaSr1− xCa xCu3O7−δ, the material becoming tetragonal at x=0.2. Ac susceptibility and dc electrical resistivity measurements as function of temperature from 10 to 300 K showed that the superconducting transition temperature Tc decreases monotonically from 84 to 75 K as the Ca concentration x increases from 0.0 to 0.3. The decrease in Tc can be attributed to the structural change taking place in EuBaSrCu3O7 as a consequence of replacement of Sr by Ca. [ABSTRACT FROM AUTHOR]

The effect of Ca doping in EuBaSrCu3O7−δ has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measurements. X-Ray diffraction analyses of the samples showed that up to 30 at.% Ca can be substituted for Sr in EuBaSrCu3O7−δ, which has orthorhombic symmetry. The orthorhombicity decreases with increase in x, in EuBaSr1−xCax Cu3O7−δ, the material becoming tetragonal at x=0.2. Ac susceptibility and dc electrical resistivity measurements as function of temperature from 10 to 300 K showed that the superconducting transition temperature T c decreases monotonically from 84 to 75K as the Ca concentration x increases from 0.0 to 0.3 The decrease in T c can be attributed to the structural change taking place in EuBaSrCu3O7 as a consequence of replacement of Sr by Ca. [ABSTRACT FROM AUTHOR]

Inorganic macrocycles remain challenging synthetic targets due to the limited number of strategies reported for their syntheses. Among these species, large fully inorganic cyclodiphosphazane macrocycles have been experimentally and theoretically highlighted as promising candidates for supramolecular chemistry. In contrast, their hybrid organic-inorganic counterparts are lagging behind due to the lack of synthetic routes capable of controlling the size and topological arrangement (i.e., folded vs unfolded) of the target macrocycle, rendering the synthesis of differently sized macrocycles a tedious screening process. Herein, we report-as a proof-of-concept-the combination of pre-arranged building blocks and a two-step synthetic route to rationally enable access a large unfolded tetrameric macrocycle, which is not accessible via conventional synthetic strategies. The obtained macrocycle hybrid cyclodiphosphazane macrocycle, cis-[μ-P(μ-N t Bu)] 2 (μ-p-OC 6 H 4 C(O)O)] 4 [μ-P(μ-N t Bu)] 2 (4), displays an unfolded open-face cavity area of 110.1 Å 2 . Preliminary theoretical host-guest studies with the dication [MeNC 5 H 4 ] 2 2+ suggest compound 4 as a viable candidate for the synthesis of hybrid proto-rotaxanes species based on phosphazane building blocks., (© 2022. The Author(s).)

Inorganic macrocycles remain largely underdeveloped compared with their organic counterparts due to the challenges involved in their synthesis. Among them, cyclodiphosphazane macrocycles have shown to be promising candidates for supramolecular chemistry applications due to their ability to encapsulate small molecules or ions within their cavities. However, further developments have been handicapped by the lack of synthetic routes to high-order cyclodiphosphazane macrocycles. Moreover, current approaches allow little control over the size of the macrocycles formed. Here we report the synthesis of high-order oxygen-bridged phosphazane macrocycles via a "3 + n cyclisation" (n = 1 and 3). Using this method, an all-P III high-order hexameric cyclodiphosphazane macrocycle was isolated, displaying a larger macrocyclic cavity than comparable organic crown-ethers. Our approach demonstrates that increasing building block complexity enables precise control over macrocycle size, which will not only generate future developments in both the phosphazane and main group chemistry but also in the fields of supramolecular chemistry., (© 2021. The Author(s).)