Visualization of flow pattern and thermal image analysis of enhanced heat transfer surface

Experimental studies on flow visualization and heat transfer measurements of finned surface in a narrow duct were carried out to understand the flow behavior and its effect on heat transfer. In this experiment, short rectangular fins were attached to a surface (endwall) with having inclination angle of 20° and exposed to air flow. Several flow visualization results reveal that horse shoe vortex was formed just at the front of the fin whereas the main longitudinal vortex was formed by the side top edge of the fin. Some important features of the vortex structure, size and flow reattachment positions were noticed from the smoke flow visualization. Detailed heat transfer distributions were discussed from the thermal image. Nusselt number shows that the finned surface achieved average heat transfer enhancement at a factor of four times than that of without fins.     

Comparative studies on the effect of duct height on heat transfer and flow behavior between co-angular and co-rotating type finned surface

This paper presents the comparative studies on the effect of duct height on heat transfer and flow behavior between co-angular and co-rotating type finned surface in duct. Experiments were performed to investigate the effect of duct height on heat transfer enhancement of a surface affixed with arrays (7 × 7) of short rectangular plate fins of a co-angular and a co-rotating type pattern in the duct. An infrared imaging system with the camera of TVS 8000 was used to measure the temperature distributions to calculate the local heat transfer coefficients of the representative fin regions. Pressure drop and heat transfer experiments were performed for both types of fin pattern varying the duct to fin height ratio (H _d/H _f) of 2.0–5.0. The friction factor calculated from the pressure drop shows that friction factor decreases with increasing the duct to fin height ratio (H _d/H _f) regardless of fin pattern and this is expected because the larger friction occurs for smaller duct to fin height ratios. Detailed heat transfer distribution gives a clear picture of heat transfer characteristics of the overall surface as well as the influence of the duct height. In addition, different flow behavior and flow structure developed by both patterns were visualized by the smoke flow visualization technique.     

Design,Synthesis and Cytotoxic Activity Evaluation of Newly Synthesized Amides-Based TMP Moiety as Potential Anticancer Agents over HepG2 Cells

A novel series of amides based TMP moiety was designed, synthesized and evaluated for their antiproliferative as well as enzyme inhibition activity. Compounds 6a and 6b showed remarkable cytotoxic activity against HepG2 cells with IC₅₀ values 0.65 and 0.92 μM, respectively compared with SAHA and CA-4 as reference compounds. In addition, compound 6a demonstrated good HDAC-tubulin dual inhibition activity as it showed better HDAC activity as well as anti-tubulin activity. Moreover, compound 6a exhibited G2/M phase arrest and pre-G1 apoptosis as demonstrated by cell cycle analysis and Annexin V assays. Further apoptosis studies demonstrated that compound 6a boosted the level of caspase 3/7. Caspase 3/7 activation and apoptosis induction were evidenced by decrease in mitochondrial permeability suggesting that activation of caspase 3/7 may occur via mitochondrial apoptotic pathway.     

1,5-Benzothiazepine Derivatives: Green Synthesis,In Silico and In Vitro Evaluation as Anticancer Agents

Considering the importance of benzothiazepine pharmacophore, an attempt was carried out to synthesize novel 1,5-benzothiazepine derivatives using polyethylene glycol-400 (PEG-400)-mediated pathways. Initially, different chalcones were synthesized and then subjected to a cyclization step with benzothiazepine in the presence of bleaching clay and PEG-400. PEG-400-mediated synthesis resulted in a yield of more than 95% in less than an hour of reaction time. Synthesized compounds 2a–2j were investigated for their in vitro cytotoxic activity. Moreover, the same compounds were subjected to systematic in silico screening for the identification of target proteins such as human adenosine kinase, glycogen synthase kinase-3β, and human mitogen-activated protein kinase 1. The compounds showed promising results in cytotoxicity assays; among the tested compounds, 2c showed the most potent cytotoxic activity in the liver cancer cell line Hep G-2, with an IC₅₀ of 3.29 ± 0.15 µM, whereas the standard drug IC₅₀ was 4.68 ± 0.17 µM. In the prostate cancer cell line DU-145, the compounds displayed IC₅₀ ranges of 15.42 ± 0.16 to 41.34 ± 0.12 µM, while the standard drug had an IC₅₀ of 21.96 ± 0.15 µM. In terms of structural insights, the halogenated phenyl substitution on the second position of benzothiazepine was found to significantly improve the biological activity. This characteristic feature is supported by the binding patterns on the selected target proteins in docking simulations. In this study, 1,5-benzothiazepines have been identified as potential anticancer agents which can be further exploited for the development of more potent derivatives.     

T3P-promoted synthesis of a series of novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones

A series of 11 novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-aryl-C-phenyl imines with thiosalicylic acid. This provides simple and ready access to N-aryl compounds in this family, which have been generally difficult to prepare.     

Azobenzene Isomerization-Induced Photomodulation of Electronic Properties of N-Heterocyclic Carbenes

Azobenzene-based protonated N-heterocyclic carbenes (NHCs), N,N’-bis(azobenzene)imidazolium chlorides (IAz-X⋅HCl; X=OMe, Br, H) were successfully synthesized and switching abilities of the attached azobenzene units along with the concomitant photoinduced generation of geometric isomers were studied. Upon irradiation with 365 nm UV light, a p-methoxy-azobenzene derivative get transformed from all-trans isomer to nearly all-cis isomer at the photostationary state. The extent of photomodulation of electronic properties in the NHC ring of the p-methoxy-azobenzene derivative is determined through the Tolman Electronic Parameter (TEP). Iridium complex, [(IAz-OMe)IrCl(CO)₂] was synthesized and infrared spectra were recorded in dichloromethane solution as film in NaCl crystals and by drop-casting in an ATR crystal. Comparison in averaged carbonyl stretching frequency between all-trans isomer ( ) and all-cis isomer ( ) indicates a significant decrement of Δ^tt–cc _av=2.7 cm⁻¹ (film) and 3.8 cm⁻¹ (ATR). Therefore, moderate to excellent enhancement of electron density (Δ^tt–cc TEP=2.3 cm⁻¹ [film] and 3.2 cm⁻¹ [ATR]) at the C-2 position of the NHC is achieved through trans→cis isomerization of the remotely placed azobenzene units. This fine phototuning of electron-donating ability at the catalytic center would pave the way to control NHC/NHC-metal catalyzed organic transformations through external stimuli.     

Semiconductor Behavior and Room Temperature Ferromagnetism in e-Beam Evaporated Co/TiO2 Multilayer Thin Films

Physics of the Solid State - The Co/TiO2 multilayer thin films have been deposited by e-beam evaporation method on glass substrates in vacuum and annealed in air at 773 K for 1 h. The crystal...     

Amphiphilic water soluble cationic ring opening metathesis copolymer as an antibacterial agent

Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC ₅₀ = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer.     

Geochemical characterization of miocene core sediments from Shahbazpur gas-wells (Bangladesh) in terms of elemental abundances by instrumental neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - Geochemical characterization of Shahbazpur structure (Bengal Foredeep) in terms of elemental abundances obtained from INAA are presented by...