Effect of jet-to-plate spacing in laminar array jets impinging

The rate of heat transfer from a plate due to impinging of an array of jets was investigated. The effect of jet-to-plate spacing in a confined array of impinging laminar square jets was investigated numerically through the solution of Navier Stokes and energy equations. The simulation is carried out for the jet-to-plate spacing between 2 B and 20 B and for jet-to-jet spacing of 4 B, where B is the jet width. Five in-line jets subjected to across-flow were used in this investigation. Also, six different ratios of jet to cross-flow velocity are simulated (0.5, 1.0, 2.5, 5, 7.5 and 10) for the jet Reynolds number of 200. The predicted results show a formation of one or two ground horseshoe vortices between the jets. In addition, a horseshoe vortex forms at different position between the orifice and impinging plates due to the interaction of two jets before they combine. The number of the ground horseshoe vortex and its size are strongly affected by the jet-to-plate spacing and by jet to cross-flow velocity ratio. The effect of jet-to-plate spacing and jet to cross-flow velocity ratio on heat transfer is presented and discussed.     

Evaluation of Antioxidant and Enzyme Inhibition Properties of Croton hirtus L’Hér. Extracts Obtained with Different Solvents

Croton hirtus L’Hér methanol extract was studied by NMR and two different LC-DAD-MSⁿ using electrospray (ESI) and atmospheric pressure chemical ionization (APCI) sources to obtain a quali-quantitative fingerprint. Forty different phytochemicals were identified, and twenty of them were quantified, whereas the main constituents were dihydro α ionol-O-[arabinosil(1-6) glucoside] (133 mg/g), dihydro β ionol-O-[arabinosil(1-6) glucoside] (80 mg/g), β-sitosterol (49 mg/g), and isorhamnetin-3-O-rutinoside (26 mg/g). C. hirtus was extracted with different solvents—namely, water, methanol, dichloromethane, and ethyl acetate—and the extracts were assayed using different in vitro tests. The methanolic extracts presented the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), and ferric reducing antioxidant power (FRAP) values. All the tested extracts exhibited inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), with a higher activity observed for dichloromethane (AChE: 5.03 and BChE: 16.41 mgGALAE/g), while the methanolic extract showed highest impact against tyrosinase (49.83 mgKAE/g). Taken together, these findings suggest C. hirtus as a novel source of bioactive phytochemicals with potential for commercial development.     

Antioxidant activities and liquid chromatography with electrospray ionization tandem mass spectrometry characterization and quantification of the polyphenolic contents of Rumex nervosus Vahl leaves and stems

In the present study, four compounds, viz. chlorogenic acid, catechin, orientin, and apigenin‐O‐acetylglycoside among 18 polyphenol compounds (17 flavonoids and one hydroxycinnamic acid derivative) were characterized for the first time in Rumex nervosus leaves and stems by using liquid chromatography with electrospray ionization tandem mass spectrometry. Method validation in terms of determination coefficient, limits of detection, and quantification were ≥ 0.9979, 0.68–1.61, and 2.27–5.38 mg/L, respectively. Accuracy, expressed as percent recovery for two spiking levels (10 and 50 mg/L), were in the range 78.9–110.6% with the exception of caffeic acid. The relative standard deviations were 1–17%. The total polyphenol content was higher by approximately two times in the leaf (1073 mg/kg fresh sample) than in the stem (519.86 mg/kg fresh sample). The antioxidant effects increased in a dose‐dependent manner, and the scavenging activities, investigated by measuring 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) scavenging activity, ferrous ions chelating activity, superoxide anion radical scavenging activity, and ferric reducing antioxidant power activity, were significant (p < 0.05) using low concentrations of the leaf extract. Overall, the present study suggests that different parts of R. nervosus have great potential for producing a range of extracts with potential applications in medicine.     

Variation of filamentation phenomenon in strongly magnetized plasma with various discharge parameters

Filamentation phenomenon is one of the most important outcomes of applying a strong magnetic field to low-pressure plasmas and dusty plasmas. In this article, the variation of filamentation phenomenon with neutral gas pressure and plasma density will be investigated using numerical simulations. It will be shown through these simulations how the formation of the filamentary patterns in the magnetized plasma results in a localized electric field structure that strongly contributes to the properties of the filamentary patterns. Based on the results of the simulations, a theoretical model is derived that relates the width of the filamentary patterns to the plasma density. The model has been successfully employed to predict the width of the patterns emerging in various simulations of the magnetized plasma.     

Photophysics and morphology of a polyfluorene donor–acceptor triblock copolymer for solar cells

We present a study of the optical, structural and device properties of a polyfluorene (PFM)‐based (PFM‐F8BT‐PFM) donor–acceptor triblock copolymer for use in an organic solar cell. Neutron reflectivity is employed to probe the vertical composition profile before and after thermal annealing while the crystallinity was examined using grazing incidence wide‐angle X‐ray. The absorption spectra and photoluminescence emission for the triblock and analogous blend of PFM with F8BT reveal a greater degree of intermixing in the triblock. However, the triblock copolymer exhibits exciplex emission, which necessitates a geminate polar pair; long‐lived exciplex states are detrimental in organic photovoltaic devices. The triplet yield in the triblock and the blend is estimated using photoinduced absorption, with the triblock copolymer generating a triplet population 20 times that of the blend. This is far from ideal as triplets are wasted states in organic photovoltaic devices and they can also act as scavengers of polarons reducing the efficiency even more. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1705–1718     

Synthesis,characterization, anti-fungi and anti-bacterial activity of new [(2-pyridyl)-3-isatin]-bishydrazone

New [(pyridine-2-carboxaldhyde)-3-isatin]-bishydrazone (cpish), [(2-acetylpyridine)-3-isatin]-bishydrazone (apish), and [(2-benzoyl pyridine)-3-isatin]-bishydrazone (bpish) have been synthesized and characterized by the elemental analysis, IR, NMR and electronic spectra. The bioefficiency of the [(2-pyridyl)-3-isatin]-bishydrazones have been examined for their in-vitro antibacterial and antifungal activity against many types of bacteria and fungal cultures which are common contaminants of the environment in Egypt and some of which are involved in human and animal diseases or in plant diseases or frequently reported from contaminated soil, water, and food substances. The results of these studies indicate that the [(2-pyridyl)-3-isatin]-bishydrazones possess notable antimicrobial properties.     

DFT (density functional theory) studies on cycloisomerization of 15–membered triazatriacetylenic macrocycle

The mechanism as well the stereochemistry of cascade cycloisomerization of 15–membered triazatriacetylenic macrocycle was investigated theoretically by using M062X/6–31+G(d,p) and M062X/LANL2DZ calculations. The results showed that the mechanism and outcome of the reaction depended on the absence and presence of a transition metal catalyst. So that, in thermal-induced condition, the reaction had to experience several suprafacial concerted reactions including Ene-reaction (DG^#=35.38 kcal/mol), Diels–Alder cycloaddition (DG^# = 17.16 kcal/mol), and sigmatropic H-shift rearrangement (DG^# = 56.21 kcal/mol) to produce diastereoselective fused cis–tetracyclic aromatic bearing a pyrrole moiety by following kinetic considerations. Also, the [2+2+2] cycloaddition mechanism was neglected in thermal–induced conditions because of high activation free Gibbs energy (DG^# = 63.90 kcal/mol). In the presence of palladium catalyst, Pd(0) formed an adduct by coordinating to C = C bonds and decreased the DG^# of the process to 29.58 kcal/mol, and consequently provided a facilitated media for the reaction to follow the [2+2+2] to produce more stable fused tetracyclic benzenoid aromatic by passing through the lower energy barrier.     

Secure OFDM with Peak-to-Average Power Ratio Reduction Using the Spectral Phase of Chaotic Signals

In this paper, a new physical layer security technique is proposed for Orthogonal Frequency Division Multiplexing (OFDM) communication systems. The security is achieved by modifying the OFDM symbols using the phase information of chaos in the frequency spectrum. In addition, this scheme reduces the Peak to Average Power Ratio (PAPR), which is one of the major drawbacks of OFDM. The Selected Mapping (SLM) technique for PAPR reduction is employed to exploit the random characteristics of chaotic sequences. The reduction with this algorithm is shown to be similar to that of other SLM schemes, but it has lower computational complexity and side information does not have to be sent to the receiver. The security of this technique stems from the noise like behavior of chaotic sequences and their dependence on the initial conditions of the chaotic generator (which are used as the key). Even a slight difference in the initial conditions will result in a different phase sequence, which prevents an eavesdropper from recovering the transmitted OFDM symbols.     

Chemical Composition,Biological Activities and In Silico Analysis of Essential Oils of Three Endemic Prangos Species from Turkey

In this study, the essential oils (EOs) obtained from three endemic Prangos species from Turkey (P. heyniae, P. meliocarpoides var. meliocarpoides, and P. uechtritzii) were studied for their chemical composition and biological activities. β-Bisabolenal (12.2%) and caryophyllene oxide (7.9%) were the principal components of P. heyniae EO, while P. meliocarpoides EO contained sabinene (16.7%) and p-cymene (13.2%), and P. uechtritzii EO contained p-cymene (24.6%) and caryophyllene oxide (19.6%), as the most abundant components. With regard to their antioxidant activity, all the EOs were found to possess free radical scavenging potential demonstrated in both DPPH and ABTS assays (0.43–1.74 mg TE/g and 24.18–92.99 mg TE/g, respectively). Additionally, while no inhibitory activity was displayed by P. meliocarpoides and P. uechtritzii EOs against both cholinesterases (acetyl- and butyryl-cholinesterases). Moreover, all the EOs were found to act as inhibitors of tyrosinase (46.34–69.56 mg KAE/g). Molecular docking revealed elemol and α-bisabolol to have the most effective binding affinity with tyrosinase and amylase. Altogether, this study unveiled some interesting biological activities of these EOs, especially as natural antioxidants and tyrosinase inhibitors and hence offers stimulating prospects of them in the development of anti-hyperpigmentation topical formulations.