The emergence of diseases and mortalities in aquaculture and development of antibiotics resistance in aquatic microbes, has renewed a great interest towards alternative methods of prevention and ...control of diseases. Nanoparticles have enormous potential in controlling human and animal pathogens and have scope of application in aquaculture. The present investigation was carried out to find out suitable nanoparticles having antimicrobial effect against aquatic microbes. Different commercial as well as laboratory synthesized metal and metal oxide nanoparticles were screened for their antimicrobial activities against a wide range of bacterial and fungal agents including certain freshwater cyanobacteria. Among different nanoparticles, synthesized copper oxide (CuO), zinc oxide (ZnO), silver (Ag) and silver doped titanium dioxide (Ag–TiO₂) showed broad spectrum antibacterial activity. On the contrary, nanoparticles like Zn and ZnO showed antifungal activity against fungi like Penicillium and Mucor species. Since CuO, ZnO and Ag nanoparticles showed higher antimicrobial activity, they may be explored for aquaculture use.
Laser cladding of Stellite 6 on stainless steel 13Cr–4Ni has been performed to study the performance of clad on solid particle erosion (SPE) and cavitation erosion at varied energy densities (from 32 ...to 52J/mm2). Results are also compared with the AISI 304 stainless steel. The cladding geometry, dilution, microstructure and variation in microhardness were also investigated with laser energy inputs. The performance of cladded surfaces was studied for solid particle erosion and cavitation erosion resistance in 3.5% NaCl solution according to ASTM standard G76-07 and ASTM G32-07 methods respectively. Results indicated that clad dilution was 3–6% (geometrically) and 4.48% (compositionally) at 32J/mm2 that increased further with laser energy density. This accompanied compositional changes in the clad such that the Fe and Ni contents increased and Co, Cr, and W were observed to reduce with variation of laser energy density from 32 to 52J/mm2. The highest hardness (705Hv) of the clad was obtained at 32J/mm2 which reduced further by enhancing the laser energy density. Stellite 6 cladding has significantly enhanced the solid particle erosion resistance of stainless steel. Cladding at 32J/mm2 showed SPE and cavitation resistance than the cladding performed at higher laser energy densities. Cavitation erosion resistance of the stainless steel in 3.5% sodium chloride solution was enhanced by >90% by laser cladding. Lower corrosion current density of 13Cr–4Ni is observed after laser cladding which further increased with laser energy density. The erosion resistance obtained can be explained on the basis of dimensionless parameter related to kinetic energy. Cavitation resistance appears related to elastic recovery after cladding.
•Stellite cladding is performed on stainless steel at 32 to 52J/mm2 laser energy density.•Lowest dilution is obtained on clad at laser energy density of 32J/mm2.•Maximum increase in solid particle erosion resistance is obtained on clad at laser energy density of 32J/mm2.•Large Increase, by 98%, in cavitation resistance of 13Cr–4Ni was obtained at 32J/mm2 laser energy density.
Performance of photonic devices critically depends upon their efficiency on controlling the flow of light therein. In the recent past, the implementation of plasmonics, two-dimensional (2D) materials ...and metamaterials for enhanced light-matter interaction (through concepts such as sub-wavelength light confinement and dynamic wavefront shape manipulation) led to diverse applications belonging to spectroscopy, imaging and optical sensing etc. While 2D materials such as graphene, MoS2 etc., are still being explored in optical sensing in last few years, the application of plasmonics and metamaterials is limited owing to the involvement of noble metals having a constant electron density. The capability of competently controlling the electron density of noble metals is very limited. Further, due to absorption characteristics of metals, the plasmonic and metamaterial devices suffer from large optical loss. Hence, the photonic devices (sensors, in particular) require that an efficient dynamic control of light at nanoscale through field (electric or optical) variation using substitute low-loss materials. One such option may be plasmonic metasurfaces. Metasurfaces are arrays of optical antenna-like anisotropic structures (sub-wavelength size), which are designated to control the amplitude and phase of reflected, scattered and transmitted components of incident light radiation. The present review put forth recent development on metamaterial and metastructure-based various sensors.
A systematic mapping of natural absorbed dose rate was carried out to assess the existing exposure situation in India. The mammoth nationwide survey covered the entire terrestrial region of the ...country comprising of 45127 sampling grids (grid size 36 km2) with more than 100,000 data points. The data was processed using Geographic Information System. This study is based on established national and international approaches to provide linkage with conventional geochemical mapping of soil. Majority (93%) of the absorbed dose rate data was collected using handheld radiation survey meters and remaining were measured using environmental Thermo Luminescent Dosimeters. The mean absorbed dose rate of the entire country including several mineralized regions, was found to be 96 ± 21 nGy/h. The median, Geometric Mean and Geometric Standard Deviation values of absorbed dose rate were 94, 94 and 1.2 nGy/h, respectively. Among the High Background Radiation Areas of the country, absorbed dose rate varied from 700 to 9562 nGy/h in Karunagappally area of Kollam district, Kerala. The absorbed dose rate in the present nationwide study is comparable with the global database.
•Mapping of gamma radiation levels carried out to assess existing exposure situation.•Nationwide survey comprised of more than 100,000 data points processed using GIS.•Mean absorbed gamma dose rate was 96 ± 21 nGy/h with median of 94 nGy/h.•Highest background radiation of 9562 nGy/h was in Karunagappally, Kerala.•This national dose rate map will help scientific community and decision makers.
This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following ...slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350°C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (εr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40K for both 1350°C and 1700°C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.
• Preparation of single-phasic polycrystalline GdMnO3 sample by the solid state sintering route.• Observation of square type P–E hysteresis loop with higher saturation and remnant polarization.• Observation of antiferromagnetic behavior at 40K in polycrystalline GdMnO3.• Possibility of room temperature application of GdMnO3 as multifunctional material.
ABSTRACT
The photoelectron sheath and floating fine positively charged dust particles constitute two-component dusty plasma in the sunlit lunar regolith’s vicinity. By including the charge ...fluctuation into photoelectron–dust dynamics, the lunar exospheric plasma is proposed to support the propagation of long-wavelength dust acoustic (DA) modes. Using the standard approach based on the dynamical equations for continuity, momentum, plasma potential, and dust charging along with Fowler's treatment of photoemission and non-Maxwellian nature of the sheath photoelectrons, the wave dispersion is derived. The dust charge variation modifies the usual DA wave dispersion and excites the ultralow frequency modes that propagate with sufficiently low phase speed. Such ultralow frequency modes are predicted as pronounced for smaller values of dust charge and sheath potential. The DA wave dispersion is also depicted as sensitive to the photoelectrons’ energy distribution within the sheath. The quantitative estimates suggest that the nominal exospheric plasma may exhibit DA waves propagating with frequencies of the order of unity.
We have investigated the accelerating behaviour of the Universe in
f
(
Q
,
T
) gravity in an isotropic and homogeneous space-time. We have initially derive the dynamical parameters in the general ...form of
f
(
Q
,
T
)
=
α
Q
m
+
β
T
(Xu et al. in Eur Phys J C 79:708, 2019) and then split it into two cases (i) one with
m
=
1
and the (ii) other with
β
=
0
. In the first case, it reduces to the linear form of the functional
f
(
Q
,
T
) and second case leads to the higher power of the nonmetricity
Q
. In an assumed form of the hyperbolic scale factor, the models are constructed and its evolutionary behaviours are studied. The geometrical parameters as well the equation of state parameter are obtained and found to be in the preferred range of the cosmological observations. Marginal variation has been noticed in the behaviour of
ω
and
ω
eff
at present time. The violation of strong energy conditions in both the cases are shown. The dynamical system analysis for the models has been performed.
Abstract
Structure and time evolution of the large-scale background and an embedded synoptic-scale monsoon depression and their interactions are studied. The depression formation is preceded by a ...cyclonic circulation around 400 hPa. The Fourier-based scale separation technique is used to isolate large (wavenumbers 0–8) and synoptic-scale (wavenumbers 12–60). The wavelength and depression center is determined objectively. The synoptic-scale depression has an average longitudinal wavelength of around 1900 km and a north–south size of 1100 km; it is most intense with a vorticity of 20.5 × 10
−5
s
−1
at 900 hPa. The strongest cold core of −3.0°C below 850 hPa and the above warm core of around 2.0°C are evident. The depression is tilted southwestward in the midtroposphere with no significant vertical tilt in the lower troposphere. The mean maximum intensity and upward motion over the life cycle of depression are in close agreement with the composite values. A strong cyclonic shear zone is developed in the midtroposphere preceding the depression. The necessary condition for barotropic (baroclinic) instability is satisfied in the midtroposphere (boundary layer). Strong northward transport of momentum by the depression against the southward shear is found. The strong growth of the MD in the lower troposphere is due to downward transfer of excess energy gained in the midtroposphere from the barotropic energy conversion and east–west direct thermal circulation as the vertical energy flux. The baroclinic interaction contributes to the maintenance of the cold core in the lower troposphere. The diabatic heating rate is computed and its role in the genesis and growth of MD is investigated.
A novel thermal plasma in-flight technique has been adopted to synthesize nanocrystalline ZnO and carbon doped nanocrystalline ZnO matrix. Transmission electron microscopy (TEM) studies on these ...samples show the average particle sizes to be around 32nm for ZnO and for carbon doped ZnO. An enhancement of saturation magnetization in nanosized carbon doped ZnO matrix by a factor of 3.8 has been found in comparison to ZnO nanoparticles at room temperature. Raman measurement clearly indicates the presence of Zn–C complexes surrounded by ZnO matrix in carbon doped ZnO. This indicates that the ferromagnetic signature in carbon doped ZnO arises from the creation of defects or the development of oxy-carbon clusters, in the carbon doped ZnO system. Theoretical studies based on density functional theory also support the experimental analyses.
► Synthesis of nanocrystalline ZnO and carbon doped ZnO matrix by inflight thermal plasma reactor. ► Enhancement of ferromagnetism in nanosized carbon doped ZnO in comparison to ZnO nanoparticles. ► Raman measurement indicates the presence of Zn–C complexes surrounded by ZnO matrix. ► Ferromagnetic signature in carbon doped ZnO arises from the development of oxy-carbon clusters. ► DFT supports experimental evidence of ferromagnetism in C doped ZnO nanoparticles.
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