The ecological footprint, a measure of human demand on earth’s ecosystems, represents the amount of biologically productive land and sea area that is necessary to supply the resources a human ...population consumes and to mitigate associated waste. This study estimates the impact of economic growth and natural resources on Pakistan’s ecological footprint using an autoregressive distributive lag (ARDL) model for long-run estimation. The empirical findings indicate that natural resources have a positive effect on an ecological footprint that deteriorates environmental quality and that natural resources help to support the environmental Kuznets hypothesis (EKC). Bidirectional causality is found between natural resources and the ecological footprint, along with a long-run causality between biocapacity and the ecological footprint. The innovative findings have important implications for policy.
Background: This study aimed to evaluate the phytochemicals screening of Erythrina suberosa (Roxb) bark and to analyze the enzymatic activities of its various organic fractions. Materials and ...Methods: Crude methanolic fraction of E. suberosa (Roxb) bark and its respective fractions were screened for the presence of different phytochemicals with different reagents. On the basis of increasing order of polarity, different organic solvents were used to obtain different fractions. Enzymatic studies were performed on crude methanolic extract of the plant. All the assays were performed under standard in vitro conditions. Results: The phytochemical analysis shows the presence of alkaloids, phenols, triterpenoids, phytosterols, and flavonoids. Phenolic compounds and flavonoids are the major constituents of the plant. In anticholinesterase assay, the percent inhibition of standard drug (eserine) was 91.27 ± 1.17 and the half maximal inhibitory concentration (IC50) was 0.04 ± 0.0001. For α-glucosidase inhibition, the IC50 value for Dichloromethane fraction was 8.45 ± 0.13, for Methanol fraction it was 64.24 ± 0.15, and for aqueous fraction it was 42.62 ± 0.17 as compared with standard IC50 that is 37.42 (acarbose). Furthermore, results show that all fractions have potential against anti-urease enzyme, but DCM fraction of crude aqueous extract has significant IC50 value (45.26 ± 0.13) than other fractions. Conclusion: Keeping in view all the results, it is evident that the plant can be used in future for formulating effective drugs against many ailments. Secondary metabolites and their derivatives possess different biological activities, for example, .g. flavonoids in cancer, asthma, and Alzheimer. Furthermore, the extracts of this plant can be used in their crude form, which is an addition to the complementary and alternative treatment strategies.
A novel green-yellow emitting Ca1.5Mg0.5Si1−xLixO4−δ:Ce3+ phosphor with high quantum efficiency and thermal stability was discovered for applications in near ultraviolet pumped white light-emitting ...diodes. Its crystal structure was determined with a single-particle diagnosis approach. The Si sites in the SiO4 tetrahedra are reported for the first time to accommodate Li+ ions. This substitution, confirmed by 6Li solid-state NMR and T.O.F. neutron powder diffraction, causes a disordered occupation of Ca/Mg in the Ca3MgSi2O8 host and favors a phase transformation at ∼330 °C, which results in the formation of the novel phosphor. The produced phosphor was efficiently excited by near UV light peaking at 365 and 410 nm and produced broad green-yellow emission with peaks at 500 and 560 nm, respectively. Its quantum efficiency reached 88.4% (internal) and 55.7% (external) under excitation at 365 nm, and 80.5% (internal) and 42.7% (external) under excitation at 410 nm, while the decrease of luminescence intensity at 200 °C was small (∼26%). A WLED lamp with a high color rendering index of Ra = 92.8 was produced with the combination of a 365 nm emitting chip with blue emitting BaMgAl10O17:Eu2+, green-yellow emitting CMSL:0.01Ce, and red emitting Sr2Si5N8:Eu2+ phosphors.
Phosphors of CaLa4Si3O13 singly- and co-doped with Ce3+ and Tb3+, which are suitable for application in white LEDs, were successfully produced by using a high temperature solid state reaction method. ...Their apatite crystalline structure as well as their photoluminescent properties both at room temperature and at higher temperatures (up to 150 °C) were experimentally determined, which also allowed the determination of the energy transfer efficiency and mechanism in the host lattice from the sensitizer Ce3+ ions to the activator Tb3+ ions. The excitation spectra of the doped phosphors exhibited an intense, broad band from 200 to 420 nm, which is a good match for the UV and near-UV chip (350–420 nm). Under excitation with UV light, two distinct luminescence bands were recorded; a blue one centered at 433 nm, which is typical for Ce3+ emission, and a green one, which peaks at 552 nm, originated from 5D4 → 7F5 transition in Tb3+.
•Both Ce3+ and Tb3+ ions occupy La3+ sites in CaLa4Si3O13 host.•The emission color shift from blue to green region in Ce3+/Tb3+ co – doped CaLa4Si3O13 phosphors.•The energy transfer efficiency is increase upto 93% with the increasing of Tb3+ concentration.•Energy transfer mechanism illustrate that dipole-dipole energy transfer are dominant from Ce3+ to Tb3+ ion.•The remaining intensity of green emission of Ce3+/Tb3+ co-doped CaLa4Si3O13 phosphors is 70% at 150 °C.
Changing morbidity and mortality due to COVID-19 across the pandemic has been linked with factors such as the emergence of SARS-CoV-2 variants and vaccination. Mutations in the Spike glycoprotein ...enhanced viral transmission and virulence. We investigated whether SARS-CoV-2 mutation rates and entropy were associated COVID-19 in Pakistan, before and after the introduction of vaccinations. We analyzed 1,705 SARS-CoV-2 genomes using the Augur phylogenetic pipeline. Substitution rates and entropy across the genome, and in the Spike glycoprotein were compared between 2020, 2021 and 2022 (as periods A, B and C). Mortality was greatest in B whilst cases were highest during C. In period A, G clades were predominant, and substitution rate was 5.25 × 10
per site per year. In B, Delta variants dominated, and substitution rates increased to 9.74 × 10
. In C, Omicron variants led to substitution rates of 5.02 × 10
. Genome-wide entropy was the highest during B particularly, at Spike E484K and K417N. During C, genome-wide mutations increased whilst entropy was reduced. Enhanced SARS-CoV-2 genome substitution rates were associated with a period when more virulent SARS-CoV-2 variants were prevalent. Reduced substitution rates and stabilization of genome entropy was subsequently evident when vaccinations were introduced. Whole genome entropy analysis can help predict virus evolution to guide public health interventions.
Novel single-phase full-color-emitting Ba
9
Lu
2
Si
6
O
24
:Ce
3+
/Mn
2+
/Tb
3+
phosphors were successfully synthesized by a high-temperature solid-state reaction method. Analysis of the X-ray ...diffractograms of the produced phosphors suggests that all the luminescence doping cations preferably occupy the Ba
2+
sites in the host lattice. Li
+
were used according to Ce
3+
and Tb
3+
concentration as a charge compensation regent. Under UV excitation, the single Ce
3+
-doped phosphor exhibits an intense blue emission band that peaks at 424 nm. In the co-doped phosphors, the experimental results suggest that an efficient energy transfer mechanism from Ce
3+
to Tb
3+
and Mn
2+
results in the generation of a green emission in the Tb
3+
-doped phosphors and a red emission in the Mn
2+
-doped ones. The triple-doped phosphors, which contained specific concentrations of Ce
3+
, Mn
2+
, and Tb
3+
ions, generated a tunable (in a wide range) white light which had good color rendering index values. Thermal behavior of the present phosphors was investigated which shows better characteristics. This result qualifies the produced powders as potential single-phase trichromatic white light-emitting phosphors.
•We propose a reconfigurable terahertz band-pass filter with an ultra-high Q factor up to 273 by using the optical tunneling effects.•The filter based on the metamaterial/VO2 hybrid structure has a ...large modulation depth of 96.4% with two broad rejection sidebands.•By tuning the thickness of cavity layer, the filter can be designed for a series of transmission wavelengths, and further accomplish the switch between the narrow band-pass filtering and wideband reflection.
Up to date, reconfigurable terahertz (THz) band-pass filters based on the design of metamaterials with vanadium dioxide (VO2) have been investigated extensively. However, VO2-based THz metamaterials with high-quality tunable narrowband transmission and good stop-band rejection have yet to be reported, which are essential for THz wave filtering components or systems. Here, we propose a reconfigurable filter in combination with a dielectric metastructure and a VO2 thin film. Utilizing the optical tunneling effects of a cavity layer, the filter has a high band-pass transmission up to 98% at 0.246 THz with a narrow bandwidth of 0.0009 THz, an ultra-high Q-factor of 273, and two broad nearly-suppressed sidebands. The transmission intensity can be modulated by the phase transition of VO2, and the modulation depth is as high as 96.4%. By efficiently tuning the cavity layer thickness, the filter can be designed for a series of transmission wavelengths and further accomplish the switch between the narrow band-pass filtering and wideband reflection. Moreover, the manipulation of the incident angle and polarization can be adopted as an additional degree to achieve a similar switching function. Our study implies a potential for developing various THz applications, where reconfigurable high-Q THz filtering is required.
For future pollution-free renewable energy production, platinum group metal (PGM)-free electrocatalysts are highly required for oxygen reduction reaction (ORR) to avoid all possible Fenton reactions ...and to make fuel cell more economical. Therefore, in this study, to overcome traditional electrocatalyst limitations, we applied facile method to synthesize robust mesoporous CrN-reduced graphene oxide (rGO) nanocomposite with MnO (thereafter, Cr/rGO composite with MnO) as an electrocatalyst by efficient one-step sol-gel method by ammonolysis at 900°C for 9 h. Synthesized porous structures of Cr/rGO nanocomposite with MnO have the highest estimated surface area of 379 m
2
·g
−1
, higher than that of the carbon black (216 m
2
·
g
cat
-
1
) support, and almost uniform pore size distribution of about 4 nm. The Cr/rGO nanocomposites with MnO exhibit enhanced electrocatalytic ORR properties with estimated high half-wave potential of 0.89 V vs. the reversible hydrogen electrode (RHE) and current density of 5.90 mA·cm
−2
, compared with that of benchmark 20% Pt/C electrode (0.84 V, 5.50 mA·cm
−2
), with noticeable methanol tolerance and significantly enhanced stability in alkaline media. Hence, the Cr/rGO nanocomposites with MnO showed superior performance to 20 wt.% Pt/C; their half-wave potentials were 50 mV high, and the limiting current density was 0.40 mA·cm
−2
high. In alkaline anion exchange membrane fuel cell (AAEMFC) setup, this cell delivers a power density of 309 mW·cm
−2
for Cr/rGO nanocomposite with MnO, demonstrating its potential use for energy conversion applications. The nanosized Cr/rGO metallic crystalline nanocomposites with MnO gave a large active surface area owing to the presence of rGO, which also has an effect on the charge distribution and electronic states. Hence, it may be the reason that Cr/rGO nanocomposites with MnO, acting as more active and more stable catalytic materials, boosted the electrocatalytic properties. The synergistic consequence in nanosized Cr/rGO composite with MnO imparts the materials' high electron mobility and thus robust ORR activity in 0.1 M of KOH solution. This potential method is highly efficient for synthesis of large-scale, non-noble-metal-based electrocatalytic (NNME) materials (i.e., Cr/rGO nanocomposite with MnO) on the gram level and is efficient in preparing novel, low-cost, and more stable non-PGM catalysts for fuel cells.
Terahertz waves are expected to be used in next-generation communications, detection, and other fields due to their unique characteristics. As a basic part of the terahertz application system, the ...terahertz detector plays a key role in terahertz technology. Due to the two-dimensional structure, graphene has unique characteristics features, such as exceptionally high electron mobility, zero band-gap, and frequency-independent spectral absorption, particularly in the terahertz region, making it a suitable material for terahertz detectors. In this review, the recent progress of graphene terahertz detectors related to photovoltaic effect (PV), photothermoelectric effect (PTE), bolometric effect, and plasma wave resonance are introduced and discussed.
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