A generalized technique for the encapsulation of nano‐sized NiO particles by styrene‐2‐hydroxyethyl methacrylate copolymer

Encapsulation of nickel oxide (NiO) particles is of great interest to the researchers as such modification produces remarkable improvement in properties and versatility in application potential. In this investigation, nanosized NiO particles were first prepared by calcination of nickel hydroxide precursor obtained using a simple liquid‐phase process. The produced NiO particles were stabilized with oleic acid and then treated with tetraethylorthosilicate to produce NiO/SiO₂ composite seed particles. Finally tri‐layered inorganic/organic composite particles were prepared by seeded copolymerization of styrene and 2‐hydroxyethyl methacrylate (HEMA) in the presence of NiO/SiO₂ composite seed particles. The produced composite particles named as NiO/SiO₂/P(S‐HEMA) were colloidally stable, and the obtained particles were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy and thermogravimetric analyses. Copyright © 2015 John Wiley & Sons, Ltd.     

Biology‐Oriented Synthesis of a Withanolide‐Inspired Compound Collection Reveals Novel Modulators of Hedgehog Signaling

Biology‐oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans‐hydrindane dehydro‐δ‐lactone motif defines the characteristic scaffold of the steroid‐like withanolides, a plant‐derived natural product class with a diverse pattern of bioactivity. A withanolide‐inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell‐based assays that monitored biological signal‐transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened.     

Correlation of size and oxygen bonding at the interface of Si nanocrystal in Si–SiO2 nanocomposite: A Raman mapping study

Raman spectroscopy/mapping is used to investigate the variation of Si phonon wavenumbers, i.e., lower wavenumber (LW ~ 495–510 cm⁻¹) and higher wavenumber (HW ~ 515–519 cm⁻¹) phonons, observed in Si–SiO₂ multilayer nanocomposite (NCp) grown using pulsed laser deposition. Sensitivity of Raman spectroscopy as a local probe to surface/interface is effectively used to show that LW and HW phonons originate at surface (Si–SiO₂ interface) and core of Si nanocrystals, respectively. The consistent picture of this understanding is developed using Raman spectroscopy monitored laser heating/annealing and cooling experiment at the site of the desired wavenumber, chosen with the help of Raman mapping. Raman spectra calculations for Si₄₁ cluster with oxygen and hydrogen termination show strong mode at 512 cm⁻¹ for oxygen terminated cluster corresponding to the vibration of surface Si atoms. This supports our attribution of LW phonons to be originating at the Si–SiO₂ surface/interface. These results along with XPS show that nature of interface (oxygen bonding) in turn depends on the size of nanocrystals and LW phonons originate at the surface of smaller Si nanocrystals. The understanding developed can conclude the ongoing debate on large variation in Si phonon wavenumbers of Si–SiO₂ NCps in the literature. Copyright © 2015 John Wiley & Sons, Ltd.     

Weighted Cebysev-Ostrowski type inequalities

In account of the famous Cebysev inequality, a rich theory has appeared in the literature. We establish some new weighted Cebysev type integral inequalities. Our proofs are of independent interest and provide new estimates on these types of inequalities.     

Some rheological properties of lyotropic liquid crystals formed by phosphated polyoxyethylene surfactants,n-hexane and water

Summary Rheological measurements have been carried out using continuous shear viscometry and creep testing on two major mesophases previously found in systems containing phosphated nonyphenol ethoxylate (PNE), phosphated fatty alcohol ethoxylate (PFE), water andn-hexane. Systems containing lamellar liquid crystals exhibited a clockwise (rheopectic) hysteresis loop on the Ferranti-Shirley cone-and-plate viscometer which increased in area with increasing water content. On the other hand, both the hexagonal liquid crystalline phase and an intermediate amorphous gel phase showed an antì-clockwise (thixotropic) hysteresis.Creep tests with an air-bearing viscometer indicated that the majority of the lamellar phase systems tested had a linear visco-elastic behavior which could generally be characterised by one Maxwell unit combined with two Voigt units.The results are discussed in relation to the effects that water produces on the probable structure of the mesomorphic structures, in particular the coiling of the polyoxyethylene chains on the surfactant molecules.

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Zusammenfassung Rheologische Messungen mit den Methoden der kontinuierlichen Scherviskosimetrie und der Kriech-Prüfung wurden an zwei neu gefundenen Haupt-Mesophasen in Systemen von phosphatisiertem Nonylphenol-Äthoxylat (PNE), phosphatisiertem Fettalkohol-Äthoxylat (PFE), Wasser undn-Hexan durchgeführt. Die Systeme mit lamellaren flüssigen Kristallen zeigten im Ferranti-Shirley Kegel-Platte-Viskosimeter eine im Uhrzeigersinne verlaufende (rheopexe) Hysteresis-Schleife, deren Fläche mit zunehmendem Wassergehalt größer wurde. Dagegen zeigten sowohl die hexagonale flüssigkristalline Phase als auch eine intermediäre amorphe Gelphase eine entgegen dem Uhrzeigersinn verlaufende (thixotrope) Hysteresis.Kriech-Versuche mit einem luftgelagerten Viskosimeter ergaben, daß die Mehrzahl der untersuchten lamellaren Systeme ein linear-viskoelastisches Verhalten zeigte, welches durch Kombination von einem Maxwell- und zwei Voigt-Elementen beschrieben werden kann.Die Ergebnisse werden im Hinblick auf die Wirkung des Wassers auf die wahrscheinliche Anordnung der mesomorphen Strukturen diskutiert, insbesondere die Verknäuelung der Polyoxyäthylen-Ketten auf die oberflächenaktiven Moleküle.

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With 4 figures and 2 tables     

Effect of 60Co γ-irradiation on structural and optical properties of thin films of Ga10Se80Hg10

Thin films of Ga₁₀Se₈₀Hg₁₀ have been deposited onto a chemically cleaned Al₂O₃ substrates by thermal evaporation technique under vacuum. The investigated thin films are irradiated by ⁶⁰Co γ-rays in the dose range of 50–150 kGy. X-ray diffraction patterns of the investigated thin films confirm the preferred crystallite growth occurs in the tetragonal phase structure. It also shows, the average crystallite size increases after γ-exposure, which indicates the crystallinity of the material increases after γ-irradiation. These results were further supported by surface morphological analysis carried out by scanning electron microscope and atomic force microscope which also shows the crystallinity of the material increases with increasing the γ-irradiation dose. The optical transmission spectra of the thin films at normal incidence were investigated in the spectral range from 190 to 1100 nm. Using the transmission spectra, the optical constants like refractive index (n) and extinction coefficient (k) were calculated based on Swanepoel’s method. The optical band gap (E_g) was also estimated using Tauc’s extrapolation procedure. The optical analysis shows: the value of optical band gap of investigated thin films decreases and the corresponding absorption coefficient increases continuously with increasing dose of γ-irradiation.     

<Emphasis Type="Italic">Q</Emphasis>-Switched Yb-Doped Fiber Ring Laser with a Saturable Absorber Based on a Graphene Polyvinyl Alcohol Film

We propose, design, and demonstrate a Q-switched ytterbium-doped fiber laser (YDFL) employing a thin graphene polyvinyl alcohol (PVA) film as a passive saturable absorber (SA). The graphene is synthesized by electrochemical exfoliation of graphite at room temperature in 1% sodium dodecyl sulfate (SDS) aqueous solution. Graphene flakes obtained from the process are mixed with PVA solution as the host polymer to produce a thin film, which acts as a passive Q-switcher in the YDFL ring cavity. The laser generates a stable pulse operating at a wavelength of 1,076.4 nm with a threshold pump power of 73.7 mW. At a maximum 980 nm pump power of 113.6 mW, the YDFL generates an optical pulse train with a repetition rate of 25.53 kHz and a pulse width of 10 μs. The maximum pulse energy of 50.9 nJ is obtained at a pump power of 109.9 mW. A higher-performance Q-switched YDFL is expected to be achieved with optimization of the graphene saturable absorber and the laser cavity.