Potential habitat modeling of endemic species is an appropriate method to maintain biodiversity,ecosystem function and rehabilitation of rangeland ecosystems.Astragalus caragana,A.cyclophyllon and ...A.podolobus are endemic in Iran＇s rangelands and some neighboring countries.The three native species could endure environmental stresses due to their distinctive ecophysiological characteristics.They play important roles in sustainable pastures production,recreation and improvement.They suffer severe threat from many factors including;grazing,agriculture and invasive exotic species.We analyzed the potential habitat of three native plant species in central Iran basing on the grid map with the resolution of 1-km.We used inventory records from field surveys,herbarium collections and 22 environmental factors to explore the environmental influences on given species distribution by Maximum entropy（Maxent） model.Maxent is a species distribution model that uses species occurrence and environmental data for predicting potential species.The results of our study indicated species occurrence has strong correlation with environmental factors such as mean temperature of wettest season,elevation and precipitation of coldest season.We evaluated the model accuracy by AUC（area under the receiver operating characteristic curve） based on an independent test data set.AUC values indicated the high power of Maxent to create potential habitat map（AUCA.caragana=0.988,AUCA.cyclophyllon=0.927,AUCA.podolobus=0.923）.It is important to consider that AUC values tend to be lower for species that have broad distribution scope,such as A.podolobus distribution.Most suitable potential habitat distributions of the three species were predicted in the western and southwestern parts of rangelands in Isfahan province.Visual comparisons of the actual distribution map of the three species with produced Maxent maps represent a good agreement.In general,the model demonstrated that the occurrence of the given species is highly probable when the elevation is between 2,200 and 3,000 m and mean temperature of wettest season less than 3°C.This model,therefore,can be applied to recognize potential sites for rangeland reclamation projects.
The photophysicochemical properties of selected fluoroquinolones in different solvents of various physical properties, including polarity and hydrogen bonding ability, were investigated using steady ...state fluorescence spectroscopy. The solvent-dependant fluorescence emission spectra of selected fluoroquinolones, namely ciprofloxacin (CIPR) and enrofloxacin (ENRO), were employed to gain insights concerning its photophysicochemical properties of interests. Interestingly, fluorescence spectra of the selected drugs exhibited structured emission spectra in nonpolar solvents such as hexane, whereas unstructured spectra were observed in more polar solvents such as alcohols and water. Also, a notable bathochromic shift in
was observed in fluorescence spectra of both drugs with increasing solvent polarity that resulted in biphasic behavior upon applying the Lippert-Mataga correlation that correspond to general and specific solvent effects. Applying the Lippert-Mataga correlation to the fluorescence spectra of CIPR and ENRO in various solvents was employed to estimate the dipole moment difference between the ground and excited states of them,
, where obtained results revealed the values of 9.4 and 16.2 Debye for the LE and ICT states of ENRO, respectively, and 8.0 and 16.2 Debye for the LE and ICT states of CIPR, respectively. Multiple linear regression analysis (MLRA) based on Kamlet-Taft equating was applied against absorption frequency (ν
abs
), emission frequency (ν
em
), Stokes shift (∆ν), and fluorescence quantum yield (Φ
f
), where obtained results revealed excellent correlation (
R
: 0.916–0.966) that are consistent with other results considering the effect of solvent polarizability, hydrogen bonding ability, and viscosity on the photophysicochemical properties of the studied fluoroquinolones.
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•DIF exhibits dual fluorosolvatochromism indicating complex solvent interactions.•Catalán’s model highlights the influence of solvent acidity, basicity, and polarizability on DIF’s ...fluorosolvatochromism.•The explicit interaction between DIF and solvent molecules suggests the formation of stable hydrogen-bonded complexes.•Both the biphenyl and salicylate moieties significantly influence DIF’s fluorosolvatochromism behavior.•Understanding DIF’s behavior may aid in mitigating drug-induced toxicity.
Understanding the photochemical behavior of a photosensitive drug through its molecular properties is crucial for assessing potential phototoxicity. In this study, we examine how the molecular microenvironment influences the physicochemical and photochemical properties of Diflunisal (DIF), an organofluorine salicylate derivative drug. To elucidate the photophysical properties of DIF, we employed absorption and fluorescence spectroscopy techniques combined with various DFT-based computational methods. The solvatochromic and fluorescence behaviors of DIF were investigated employing various neat solvents of various polarity and hydrogen bonding (HB) capabilities. The molecular behavior of DIF exhibited mixed fluorosolvatochromism, where a negative fluorosolvatochromism is noted as solvent polarity increases, where DIF exhibited positive fluorosolvatochromism within the examined set of protic polar solvents. These fluorosolvatochromic behaviors suggest that a combination of factors, including solvent polarity, hydrogen bonding capacity, and specific solvation effects, influences the fluorosolvatochromic properties of DIF. To elucidate the impact of specific and non-specific interactions between DIF and solvent on the fluorosolvatochromism of DIF, we utilized Catalán’s four empirical scales model. The results revealed that the solvent’s acidity, basicity, and polarizability had approximately equivalent and notable impacts on the fluorosolvatochromic behavior of DIF. For a molecular-level explanation of the experimental spectral properties, we employed DFT and TD-DFT/B3LYP/6–31 + G(d) computational methods, incorporating the IEFPCM implicit solvation approach. It is also revealed that the negative fluorosolvatochromism of DIF is attributed to the solvent’s impact on the main electronic transition, namely HOMO → LUMO. It is revealed as well that not only the salicylate moiety is affected by the solvent, but also the biphenyl moiety can exhibit a major contribution to the observed behavior. The results presented here offer insights into the photochemical behavior of DIF within various microenvironments at the molecular level. This understanding could inform future endeavors aimed at mitigating induced toxicity and side effects of DIF.
Sleep strongly affects synaptic strength, making it critical for cognition, especially learning, and memory formation. Whether and
sleep deprivation modulates human brain physiology and cognition is ...not well understood. Here we examined how overnight sleep deprivation vs overnight sufficient sleep affects (a) cortical excitability, measured by transcranial magnetic stimulation (TMS), (b) inducibility of LTP- and-LTD-like plasticity via transcranial direct current stimulation (tDCS), and (c) learning, memory and attention. The results suggest that sleep deprivation upscales cortical excitability due to enhanced glutamate-related cortical facilitation and decreased and/or reversed GABAergic cortical inhibition. Furthermore, tDCS-induced LTP-like plasticity abolishes while the inhibitory LTD-like plasticity converts to excitatory LTP-like plasticity under sleep deprivation. This is associated with increased EEG theta oscillations due to sleep pressure. Finally, we show that learning and memory formation, behavioral counterparts of plasticity, and working memory and attention, which rely on cortical excitability, are impaired during sleep deprivation. Our data suggest that upscaled brain excitability, and altered plasticity, due to sleep deprivation, are associated with impaired cognitive performance.
Abstract
We conducted an optical monitoring survey of the Sagittarius dwarf irregular galaxy (SagDIG) during the period of 2016 June–2017 October, using the 2.5 m Isaac Newton Telescopeat La Palama. ...Our goal was to identify long-period variable stars (LPVs), namely, asymptotic giant branch stars (AGBs) and red supergiant stars, to obtain the star formation history of isolated, metal-poor SagDIG. For our purpose, we used a method that relies on evaluating the relation between luminosity and the birth mass of these most evolved stars. We found 27 LPV candidates within 2 half-light radii of SagDIG. 10 LPV candidates were in common with previous studies, including one extreme-AGB (x-AGB). By adopting the metallicity
Z
= 0.0002 for older populations and
Z
= 0.0004 for younger ages, we estimated that the star formation rate changes from 0.0005 ± 0.0002
M
⊙
yr
−1
kpc
−2
(13 Gyr ago) to 0.0021 ± 0.0010
M
⊙
yr
−1
kpc
−2
(0.06 Gyr ago). Like many dwarf irregular galaxies, SagDIG has had continuous star formation activity across its lifetime, though with different rates, and experiences an enhancement of star formation since
z
≃ 1. We also evaluated the total stellar mass within 2 half-light radii of SagDIG for three choices of metallicities. For metallicity
Z
= 0.0002 and 0.0004, we estimated the stellar mass
M
*
= (5.4 ± 2.3) × 10
6
and (3.0 ± 1.3) × 10
6
M
⊙
, respectively. Additionally, we determined a distance modulus of
μ
= 25.27 ± 0.05 mag, using the tip of the red giant branch.
•New supramolecular Cu(II) immobilized on a magnetic modified GO nanosheets, with appropriate geometry of ligands for stronger chealation, was prepared by using the Click Chemistry concept.•The ...Cu(II)/mGO-TA-Me-BTA nanocomposite was examined for the synthesis of diverse derivatives of diaryl ethers.•The required Cu(I) species were obtained by in situ reduction of the Cu(II) ones using 10 mol% loading of sodium ascorbate in water.•The obtained catalytic system was found to exhibit exceptional catalytic activity for the activation of C(sp2)‒X bonds in the Ullman-type C‒O coupling of various substituted phenols.•C(sp2)‒I and C(sp2)‒Br and even less reactive C(sp2)‒Cl bonds were smoothly involved in the reaction to afford the corresponding diaryl ethers.•Moderate to excellent yield (78 % up to 93 %) of the corresponding diaryl ethers were formed under mild conditions for chloro‑ and iodo/bromo arenes, respectively.
In the present research, the new supramolecular Cu(II) species immobilized on a magnetic benzotriazole-grafted GO nanosheets (CuO/mGO-TA-Me-BTA), with appropriate geometry of ligands for stronger chealation, was fabricated by using the Click Chemistry concept as a new magnetic nanocomposite. The obtained nanomaterial was characterized by using different spectroscopic, microscopic or analytic techniques and methods such as FT-IR, EDX, XRD, FESEM, elemental mapping, TGA-DTG, AAS and VSM. Furthermore, an attempt has been made for efficient synthesis of diverse derivatives of diaryl ethers in the presence of in situ produced heterogeneous Cu(I) species supported on the modified GO nano-structured catalyst by using 10 mol% loading of sodium ascorbate (NaAsc) in water. In situ reduction of heterogeneous Cu(II) species was found to exhibit exceptional catalytic activity for the activation of C(sp2)‒I and C(sp2)‒Br and even less reactive C(sp2)‒Cl bonds in the Ullman-type C‒O coupling of various substituted phenols and iodo/bromo/chloro arenes in the presence of cesium carbonate and water. Moderate to excellent yields (78 % up to 93 %) of the corresponding diaryl ethers were formed under mild conditions for chloro‑ and bromo/iodo- arenes, respectively. High performance as well as easy recoverability and reusability for at least five times make the reduced CuO/mGO-TA-Me-BTA a robust catalytic system in comparison with other conventional heterogeneous and homogeneous catalysts containing Cu or palladium species. To the best of our knowledge, this is the first application of in situ reduction of heterogeneous Cu(II) species in the C‒X activation for the Ullman-type C‒O coupling reaction. It can address the problem of residual transition metals remaining in the synthesis of diaryl ethers, especially the biologically active compounds.
The novel supramolecular Cu(II) species immobilized on a magnetic benzotriazole-grafted GO nanosheets (CuO/mGO-TA-Me-BTA), with appropriate geometry of ligands for stronger chealation, was fabricated by using the Click Chemistry concept as a new magnetic nanocomposite. Furthermore, an attempt has been made for efficient synthesis of diverse derivatives of diaryl ethers in the presence of in situ produced heterogeneous Cu(I) species supported on the modified GO nano-structured catalyst by using 10 mol% loading of sodium ascorbate (NaAsc) in water. In situ reduction of heterogeneous Cu(II) species was found to exhibit exceptional catalytic activity for the activation of C(sp2)‒I and C(sp2)‒Br and even less reactive C(sp2)‒Cl bonds in the Ullman-type C‒O coupling of various substituted phenols and iodo/bromo/chloro arenes in the presence of cesium carbonate and water. To the best of our knowledge, this is the first application of in situ reduction of heterogeneous Cu(II) species in the C‒X activation for the Ullman-type C‒O coupling reaction. It can address the problem of residual transition metals remaining in the synthesis of diaryl ethers, especially the biologically active compounds. Display omitted
Isocyanurate bridging periodic mesoporous organosilica (PMO-ICS) was shown to be a highly active and efficient recyclable catalyst for the three-component synthesis of imidazole derivatives from ...benzoin, different aldehydes and ammonium acetate under mild reaction conditions in short reaction times and good to excellent yields in EtOH. Also, benzimidazole derivatives were efficiently prepared from
o
-phenylenediamine and different aldehydes in the presence of PMO-ICS. Moreover, the catalyst was also recovered and reused at least four times without a significant decrease in its activity. The PMO-ICS catalyst was characterized by Fourier transformer infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA), powder X-ray diffraction (XRD) and nitrogen adsorption–desorption isotherm (NADI) techniques as well as field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Compared to the classical methodologies, this method illustrated significant advantages including low loading of the catalyst, avoiding the use of toxic transition metals or reactive reagents for modification of the catalytic activity, short reaction times, high to excellent yields, easy separation and purification of the products, and reusability of the catalyst.
Abstract
We present a photometric study of the resolved stellar populations in Andromeda IX (And IX), the closest satellite to M31, a metal-poor and low-mass dwarf spheroidal galaxy. We estimate a ...distance modulus of
24.56
−
0.15
+
0.05
mag based on the tip of the red giant branch. By probing the variability of asymptotic giant branch stars, we study the star formation history of And IX. We identified 50 long-period variables (LPVs) in And IX using the Isaac Newton Telescope in two filters, the Sloan
i
′
and Harris
V
. In this study, we selected LPVs within two half-light radii with amplitudes in the range of 0.2–2.20 mag. It is found that the peak of star formation reaches ∼8.2 ± 3.1 × 10
−4
M
⊙
yr
−1
at ≈6 Gyr ago. Our findings suggest an outside-in galaxy formation scenario for And IX with a quenching occurring
3.65
−
0.13
+
1.52
Gyr ago with a star formation rate (SFR) in the order of 2.0 × 10
−4
M
⊙
yr
−1
at redshift <0.5. We calculate the total stellar mass by integrating the SFR within two half-light radii ∼3.0 × 10
5
M
⊙
. By employing spectral energy distribution fitting for the observed LPVs in And IX, we evaluate a mass-loss rate in the range of 10
−7
≤
M
̇
≤ 10
−5
M
⊙
yr
−1
. Finally, we show that the total mass deposition to the interstellar medium (ISM) is ∼2.4 × 10
−4
M
⊙
yr
−1
from the C- and O-rich types of dust-enshrouded LPVs. The ratio of the total mass returned to the ISM by LPVs to the total stellar mass is ∼8.0 × 10
−10
yr
−1
, and so at this rate it would take ∼1 Gyr to reproduce this galaxy.
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A new propylsulfonic acid-anchored isocyanurate bridging periodic mesoporous organosilica (PMO-ICS-Pr-SO3H) was prepared and shown to be a highly efficient recyclable nanoporous ...catalyst for the one-pot synthesis of bis(indolyl)methane derivatives in good to excellent yields from indole and different aldehydes in EtOH under mild reaction conditions in short reaction times. Moreover, the nanoporous catalyst was recovered and reused at least four times without significant decrease in its catalytic activity. The PMO-ICS-Pr-SO3H catalyst was characterizred by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA) and N2 adsorption–desorption isotherms techniques as well as field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) spectroscopy. Compared to the classical methodologies, this method illustrated significant advantages including low loading of the catalyst, high to excellent yields, short reaction times, avoiding the use of toxic transition metals or reactive reagents for modification of the catalytic activity, easy separation and purification of the products, and reusability of the catalyst.
•PVP-capped CdS NPs exhibited unique property of optical absorption in visible region.•Capping the NPs with PVP increased their photocatalytic efficiency by twofolds.•Photocatalytic activity of ...PVP-capped CdS NPs improved by mixing with PVP-capped ZnS.•The physical mixture with 20% of PVP-capped ZnS NPs was efficient for degradation.
Photocatalysis based on semiconductor quantum dots which utilize the solar energy can be used for the elimination of pollutants from aqueous media and applied for water purification. Degradation of dyes is a standard method to check the photocatalytic activity of any type of photocatalyst. In this paper polyvinyl pyrrolidone (PVP)-capped ZnS and CdS nanoparticles were prepared by a simple microwave irradiation method and studied in detail for their photocatalytic activity in visible range. The obtained nanoparticles were characterized by XRD, TEM, UV–Vis and EDX. The prepared PVP-capped ZnS and CdS nanoparticles have average sizes of ∼5.1 and 18.3nm with cubic and hexagonal crystalline structures, respectively. PVP capped CdS nanoparticles exhibited a unique property of optical absorption in visible region with a wave length below than 460nm followed by a clear long tail up to 700nm and showed excellent activity toward degradation of dye under visible light illumination. The photocatalytic activity of PVP-capped CdS nanoparticles was found to be improved by mixing with appropriate amount of PVP-capped ZnS nanoprticles. From the study of variation in weight percentages of PVP-capped ZnS nanoparticles, the physical mixture with 20% of PVP-capped ZnS nanoparticles was found to be very efficient for degradation of methylene blue. In this case the degradation efficiency after 6h illumination was about 81%.
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