Synthesis and pharmacological evaluation of novel 1-(piperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one derivatives as potential antimicrobial agents

Novel compounds of biological interest were synthesized by in situ reduction of Schiff’s base of 5,6-dimethoxy indanone and 1-(piperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one in the presence of Ti(OiPr)₄ and NaBH₃CN. Further alkylation using different alkyl/aryl halides in the presence of NaH in DMF gave a series of novel compounds. A formation of newly synthesized compounds was confirmed on the basis of their spectral and elemental analysis. Further these compounds were screened for their antimicrobial activity and found to have promising antibacterial and antifungal activity.     

Synthesis and antimicrobial evaluation of 1,3,4-oxadiazole-based chalcone derivatives

A series of chalcones-bearing 1,3,4-oxadiazole derivatives was synthesized as novel bio-active antimicrobial agents against multidrug-resistant bacteria and fungi. The lead compounds (Z)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)-N-(4-(3-(aryl)acryloyl)phenyl)acetamides 5a–n were synthesized via acid-catalyzed aldol condensation (SOCl₂) by reacting N-(4-acetylphenyl)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)acetamide (4) with differently substituted aldehydes. Compound (4) was obtained by reacting 5-(3-nitrophenyl)-1,3,4-oxadiazole-2-thiol (2) with N-(4-acetylphenyl)-2-chloroacetamide (3) in the presence of K₂CO₃. The intermediates (2) and (3) were synthesized simultaneously from 3-nitrobenzohydrazide (1) and 4-aminoacetophenone, respectively. The formation of intermediates and targeted compounds were confirmed for their structure by means of various spectral–analytical techniques like IR, ¹H NMR, ¹³C NMR, elemental analysis, and mass spectra. Antimicrobial properties of all the synthesized compounds have been evaluated against broad panel of bacteria and fungi.     

Influence of Test Conditions on Sliding Wear Performance of High Velocity Air Fuel-Sprayed WC–CoCr Coatings

Sliding wear performance of thermal spray WC-based coatings has been widely studied. However, there is no systematic investigation on the influence of test conditions on wear behaviour of these coatings. In order to have a good understanding of the effect of test parameters on sliding wear test performance of HVAF-sprayed WC–CoCr coatings, ball-on-disc tests were conducted under varying test conditions, including different angular velocities, loads and sliding distances. Under normal load of 20 N and sliding distance of 5 km (used as ‘reference’ conditions), it was shown that, despite changes in angular velocity (from 1333 rpm up to 2400 rpm), specific wear rate values experienced no major variation. No major change was observed in specific wear rate values even upon increasing the load from 20 N to 40 N and sliding distance from 5 km to 10 km, and no significant change was noted in the prevailing wear mechanism, either. Results suggest that no dramatic changes in applicable wear regime occur over the window of test parameters investigated. Consequently, the findings of this study inspire confidence in utilizing test conditions within the above range to rank different WC-based coatings.     

The Relationship of Visiting Insect Diversity and Density of Valeriana jatamansi with Increasing Altitude in Western Himalaya

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - In light of the recent evidences that pollinators have a significant implication for maintenance of...     

Decoding ultrafast polarization responses in lead halide perovskites by the two-dimensional optical Kerr effect

The ultrafast polarization response to incident light and ensuing exciton/carrier generation are essential to outstanding optoelectronic properties of lead halide perovskites (LHPs). A large number of mechanistic studies in the LHP field to date have focused on contributions to polarizability from organic cations and the highly polarizable inorganic lattice. For a comprehensive understanding of the ultrafast polarization response, we must additionally account for the nearly instantaneous hyperpolarizability response to the propagating light field itself. While light propagation is pivotal to optoelectronics and photonics, little is known about this in LHPs in the vicinity of the bandgap where stimulated emission, polariton condensation, superfluorescence, and photon recycling may take place. Here we develop two-dimensional optical Kerr effect (2D-OKE) spectroscopy to energetically dissect broadband light propagation and dispersive nonlinear polarization responses in LHPs. In contrast to earlier interpretations, the below-bandgap OKE responses in both hybrid CH₃NH₃PbBr₃ and all-inorganic CsPbBr₃ perovskites are found to originate from strong hyperpolarizability and highly anisotropic dispersions. In both materials, the nonlinear mixing of anisotropically propagating light fields results in convoluted oscillatory polarization dynamics. Based on a four-wave mixing model, we quantitatively derive dispersion anisotropies, reproduce 2D-OKE frequency correlations, and establish polarization-dressed light propagation in single-crystal LHPs. Moreover, our findings highlight the importance of distinguishing the often-neglected anisotropic light propagation from underlying coherent quasiparticle responses in various forms of ultrafast spectroscopy.

Understanding the ultrafast polarization response to light fields and the subsequent generation of charge carriers or excitons is key to establishing the photophysical mechanisms in the excellent optoelectronic material system of lead halide perovskites (LHPs) (1). The two ionic polarization contributions by the reorientational motion of organic cations and the deformation of the inorganic cages have been discussed within dynamic screening models (2–4) and large polaron formation (5), respectively and jointly, whereas the immediate electronic polarization response to the light field itself has been neglected so far. In many optoelectronic applications, nevertheless, not only charge carrier transport but also light propagation right below the bandgap is essential. In LHP nanowire lasers, the lasing modes are known to be redshifted from excitonic resonances due to efficient coupling to plasmon emission (6). In LHP-based exciton–polariton devices, light–matter coupling redshifts the hybrid state on the lower polariton branch (7). Propagation of subgap light is known to boost the efficiency of LHP photovoltaic cells and light-emitting devices by the so-called “photon recycling” (8). Light propagation strongly influences the function of LHP photonic devices in general (9, 10). A key feature of light propagation near the bandgap is its strong photon energy dependence, as is obvious from the classic Lorentzian model for the dielectric function near an optical resonance (11). However, most photophysical experiments probing carrier/exciton formation, screening, scattering, and nonlinear optical responses employ ultrashort excitation pulses with inherently broad energy distribution and thus convoluted spectral responses. Here, we develop a Fourier-transform-based laser spectroscopy technique, two-dimensional optical Kerr effect (2D-OKE), to investigate light propagation and nonlinear polarization responses directly in the time domain with superior excitation energy resolution near the electronic bandgap.The third-order nonlinear electric polarization P(3) serves as an in situ probe of a material’s polarizability and governs the ultrafast macroscopic response to an incident light field. This is employed in a variety of spectroscopies, such as (magneto-) OKE (12, 13), coherent phonon spectroscopy (14, 15), and four-wave mixing (FWM) in general (11). Recently, OKE has been applied to LHP single crystals: Below the bandgap, the dominating nonoscillatory Kerr response of MAPbBr₃ (MA = CH₃NH₃) compared to its all-inorganic counterpart CsPbBr3 was previously attributed to the transient polarization anisotropy caused by liquidlike reorientation dynamics of organic cations (2) and lattice disorder (5). The exponentially decaying responses with above-gap excitations were discussed in relation to polaron formation in both materials (5). Interestingly, for excitation energies close to the bandgap in CsPbBr₃ at room temperature, time-resolved OKE reveals complex oscillatory features. Such oscillatory transient birefringence signals are usually attributed to coherently excited collective modes, such as phonons (15–17) or magnons (18, 19), but the strong dependence of the oscillatory frequency on pump-photon energy in OKE seems to contradict these origins in LHPs (5). In this work, we unveil a unified source for the Kerr responses in single-crystal LHPs by tracing contributions from hyperpolarizability and the peculiar light propagation close to electronic transitions.     

Variation in stated management of acute myocardial infarction in five countries

We examined the variation in stated practice in the management of acute myocardial infarction (AMI) among doctors in Australia, Brazil, Chile, India and Thailand. Hospitals were identified as primary, secondary or tertiary by investigators from around their own region. All doctors within each hospital who would be expected to treat patients with AMI were asked to indicate which investigations and treatments they would offer to a patient with an AMI who develops angina on Day 3 after admission. The numbers of hospitals ranged from 5 to 26 per country, and doctor response rates varied from 70 to 100%. Within-country variation was large, and statistically significant variations were seen between countries in the use of most interventions. The large variation both between and within a range of countries across the economic spectrum suggests a widespread need for agreement about what constitutes appropriate management after AMI.