Simulative investigation for third order-IM terms in multi-tone RoF system

A multi-tone radio over fiber (RoF) system design for three RF signals has been investigated for different modulation techniques like direct and external modulation with EDFA and SOA amplification techniques. Frequency response has been studied including the effects of third order intermodulation terms. Frequency separation between the modulating tones has been varied to study its impact on received carrier power. The performance in terms of electrical RF power of three receiving channels at different frequency separations using different amplification techniques have been measured and compared. An improvement in the received RF power and IM suppression has been observed by using an external modulation based system with EDFA amplifier.     

Effects of Core‐modification on Porphyrin Sensitizers to the Efficiencies of Dye‐sensitized Solar Cells

To study dye‐sensitized solar cells (DSSCs) with core‐modified porphyrins as the sensitizing dyes, three porphyrins with an ethynyl benzoic acid as an anchoring group are prepared. The properties of free‐base regular porphyrin (N4), thiaporphyrin (N3S) and oxaporphyrin (N3O) were thoroughly studied by spectroscopic methods, DFT calculations, and photovoltaic measurements. Replacing one of the porphyrinic core nitrogen atoms by oxygen or sulfur considerably changes the absorption spectra. The Soret band of the N3O and N3S observed bathochromic shifts of 3‐9 nm while the Q band reaches 700 nm to the near‐infrared region. The overall conversion efficiencies of the DSSCs based on these porphyrins are in the order N4 (3.66%) ? N3S (0.22%) > N3O (0.01%). The time‐correlated single photon counting observed short fluorescence lifetimes for N3O adsorbed both on TiO₂ and Al₂O₃ which explicates the poor efficiency of DSSC using N3O as the photosensitizer.     

Determination of multi-element profiles of soil at Visakhapatnam using EDXRF technique

In the present study attempt has been made to generate elemental profile database for major sources of soil pollution, specific to Visakhapatnam. Representative road dust and soil samples from major industrial locations were collected and analyzed for various metals distribution using EDXRF. Analysis results indicate that V and Ni were predominant at PR and Zn was found to be dominating in road dust samples. Higher concentration of Arsenic was observed at TPP as compared to all other sites. Cr was found to be dominating at TPP and SP. I _geo calculations suggest that soil is highly contaminated with heavy metal pollutants.     

Flexible and Rigid Amine‐Functionalized Microporous Frameworks Based on Different Secondary Building Units: Supramolecular Isomerism,Selective CO2 Capture,and Catalysis

We report the synthesis, structural characterization, and porous properties of two isomeric supramolecular complexes of ([Cd(NH₂?bdc)(bphz)_0.5]?DMF?H₂O}_n (NH₂?bdc=2‐aminobenzenedicarboxylic acid, bphz=1,2‐bis(4‐pyridylmethylene)hydrazine) composed of a mixed‐ligand system. The first isomer, with a paddle‐wheel‐type Cd₂(COO)₄ secondary building unit (SBU), is flexible in nature, whereas the other isomer has a rigid framework based on a μ‐oxo‐bridged Cd₂(μ‐OCO)₂ SBU. Both frameworks are two‐fold interpenetrated and the pore surface is decorated with pendant ?NH₂ and ?N?N? functional groups. Both the frameworks are nonporous to N₂, revealed by the type II adsorption profiles. However, at 195 K, the first isomer shows an unusual double‐step hysteretic CO₂ adsorption profile, whereas the second isomer shows a typical type I CO₂ profile. Moreover, at 195 K, both frameworks show excellent selectivity for CO₂ among other gases (N₂, O₂, H₂, and Ar), which has been correlated to the specific interaction of CO₂ with the ?NH₂ and ?N?N? functionalized pore surface. DFT calculations for the oxo‐bridged isomer unveiled that the ?NH₂ group is the primary binding site for CO₂. The high heat of CO₂ adsorption (ΔH_ads=37.7 kJ mol^?1) in the oxo‐bridged isomer is realized by NH₂???CO₂/aromatic π???CO₂ and cooperative CO₂???CO₂ interactions. Further, postsynthetic modification of the ?NH₂ group into ?NHCOCH₃ in the second isomer leads to a reduced CO₂ uptake with lower binding energy, which establishes the critical role of the ?NH₂ group for CO₂ capture. The presence of basic ?NH₂ sites in the oxo‐bridged isomer was further exploited for efficient catalytic activity in a Knoevenagel condensation reaction.     

Determination of guaifenesin from spiked human plasma using RP-HPLC with UV detection

A rapid, simple, selective and specific high performance liquid chromatography (HPLC) method with UV detection (230 nm) was developed and validated for estimation of guaifenesin from spiked human plasma. The analyte and internal standard (eplerenone) were extracted with dichloromethane. The chromatographic separation was performed on HiQSil C 18HS column (250 × 4.6 mm, 5 μm) with a mobile phase of methanol: water (60: 40%, v/v) at a flow rate of 1 mL/min. Guaifenesin was well resolved from plasma constituents and internal standard. The calibration curve was linear in the range of 100–3200 ng/mL. The heteroscedasticity was minimized by using weighted least square regression with weighing factor of 1/x. The intra- and inter-day % RSD was less than 15. Results of recovery studies prove the extraction efficiency. Stability data indicated that guaifenesin was stable in plasma after three freeze thaw cycles and upon storage at ?20°C for 30 days.     

Total Synthesis of Δ12‐Prostaglandin J3, a Highly Potent and Selective Antileukemic Agent

A catalytic asymmetric total synthesis of the potent and selective antileukemic Δ¹²‐prostaglandin J₃ (Δ¹²‐PGJ₃) is described. The convergent synthesis proceeded through intermediates 2 and 3 , formed enantioselectively from readily available starting materials and coupled through an aldol reaction followed by dehydration to afford stereoselectively the cyclopentenone alkylidene structural motif of the molecule.     

Growth pattern and electronic properties of acetonitrile clusters: a density functional study

We report a systematic theoretical study on the growth pattern and electronic properties of acetonitrile clusters [(CH(3)CN)(n) (n = 1, 9, 12)] using density functional approach at the B3LYP6-31++G(d,p) level. Although we have considered a large number of configurations for each cluster, the stability of the lowest energy isomer was verified from the Hessian calculation. It is found that the lowest energy isomer of the dimer adopts an antiparallel configuration. For trimer and tetramer, cyclic ring structures were found to be favored over the dipole stabilized structure. In general, it is found that the intermolecular CH...N interactions play a significant role in the stabilization of the cyclic layered geometry of acetonitrile clusters. A critical comparison between trimer and tetramer clusters suggests that the three member cyclic ring is more stable than four member rings. The growth motif for larger clusters (n = 5-9, 12) follows a layered pattern consisting of three or four membered rings, which, in fact, is used as the building block. Based on the stability analysis, it is found that clusters with an even number of molecular entities are more stable than the odd clusters, except trimer and nonamer. The exceptional stability of these two clusters is attributed to the formation of trimembered cyclic rings, which have been found to form the building blocks for larger clusters.     

Dynamic Covalent Self-sorting in Molecular and Polymeric Architectures Enabled by Spiroborate Bond Exchange

Self-sorting is commonly observed in complex reaction systems, which has been utilized to guide the formation of single major by-design molecules. However, most studies have been focused on non-covalent systems, and using self-sorting to achieve covalently bonded architectures is still relatively less explored. Herein, we first demonstrated the dynamic nature of spiroborate linkage and systematically studied the self-sorting behavior observed in the transformation between spiroborate-linked well-defined polymeric and molecular architectures, which is enabled by spiroborate bond exchange. The scrambling between a macrocycle and a 1D helical covalent polymer led to the formation of a molecular cage, whose structures are all unambiguously elucidated by single-crystal X-ray diffraction. The results indicate that the molecular cage is the thermodynamically favored product in this multi-component reaction system. This work represents the first example of a 1D polymeric architecture transforming into a shape-persistent molecular cage, driven by dynamic covalent self-sorting. This study will further guide the design of spiroborate-based materials and open the possibilities for the development of novel complex yet responsive dynamic covalent molecular or polymeric systems.     

Catalytic Hydrosilylation of Imines by Aluminum Hydride Cations

In this work, the catalytic activity of electronically unsaturated three coordinated aluminum hydride cations [ L AlH]⁺[HB(C₆F₅)₃]⁻ ( 1 ) and [ L AlH]⁺[B(C₆F₅)₄]⁻ ( 2 ) in hydrosilylation of imines has been disclosed ( L ={(2,6-ⁱPr₂C₆H₃N)P(Ph₂)}₂N). A variety of organo-silanes such as Et₃SiH, MePhSiH₂, PhSiH₃, TMDSO, and PHMS are screened in this endeavour. The amines as products of catalysis were obtained in good to excellent yields after the hydrolysis of silylamine intermediates. Further, a series of controlled experiments systematically designed to investigate the underlying mechanistic pathway through multinuclear NMR analysis showed Lewis adduct formation between cationic aluminum centre and the imine nitrogen, which subsequently undergoes reaction with silane to afford the product. The hydrosilylation of imine performed with Et₃SiH using catalyst 1 with a loading of 2 mol % at 60 °C occurs smoothly. Whereas 2 led to the product formation with Et₃SiH only when used in stoichiometric quantity. Further, to investigate this unique behaviour of 1 NMR investigations were performed and revealed that the anion in 1 competes for hydride delivery and in-situ generates B(C₆F₅)₃ that cooperatively reinforces the catalytic activity of 1 .