Browsing by Subject "Concentration (process)"

Now showing 1 - 9 of 9

Open Access
Chemical concentration map building through bacterial foraging optimization based search algorithm by mobile robots
(IEEE, 2010) Turduev, M.; Kırtay, Murat; Sousa P.; Gazi V.; Marques L.
In this article we present implementation of Bacterial Foraging Optimization algorithm inspired search by multiple robots in an unknown area in order to find the region with highest chemical gas concentration as well as to build the chemical gas concentration map. The searching and map building tasks are accomplished by using mobile robots equipped with smart transducers for gas sensing called "KheNose". Robots perform the search autonomously via bacterial chemotactic behavior. Moreover, simultaneously the robots send their sensor readings of the chemical concentration and their position data to a remote computer (a base station), where the data is combined, interpolated, and filtered to form an real-time map of the chemical gas concentration in the environment. ©2010 IEEE.
Open Access
Complexing agent effect on the stoichiometric ratio of the electrochemically prepared CuInSe2 thin films
(Elsevier, 2007) Beyhan, S.; Süzer, Şefik; Kadırgan, F.
The electrodeposition of CuInSe2 is investigated to improve the stoichiometric properties of CuInSe2 layers on indium tin oxide (ITO)-coated glass substrates and to develop one-step electrodeposition method for solar cell applications. XPS was utilized for the characterization of the surface properties of CuInSe2 layers. The influence of the complexing agent, e.g. benzotriazole, bulk concentration of Cu and Se and deposition potentials on the stoichiometric properties, are discussed. © 2007 Elsevier B.V. All rights reserved.
Open Access
The formation and characterization of cyclodextrin functionalized polystyrene nanofibers produced by electrospinning
(2009) Uyar, Tamer; Havelund, R.; Hacaloglu J.; Zhou X.; Besenbacher F.; Kingshott P.
Polystyrene (PS) nanofibers containing the inclusion complex forming beta-cyclodextrin (β-CD) were successfully produced by electrospinning aimed at developing functional fibrous nanowebs. By optimization of the electrospinning parameters, which included varying the relative concentration of PS and β-CD in the solutions, bead-free fibers were produced. Homogeneous solutions of β-CD and PS in dimethylformamide (DMF) were used with concentrations of PS varying from 10% to 25% (w/v, with respect to DMF), and β-CD concentrations of 1% to 50% (w/w, with respect to PS). The presence of β-CD facilitated the production of bead-free PS fibers even from lower polymer concentrations as a result of the higher conductivity of the PS/CD solutions. The morphology and the production of bead-free PS/CD fibers were highly dependent on the β-CD contents. Transmission electron microscope (TEM) and atomic force microscope (AFM) images showed that incorporation of β-CD yielded PS fibers with rougher surfaces. Thermogravimetric analysis (TGA) and direct insertion probe pyrolysis mass spectroscopy (DP-MS) results confirmed the presence of β-CD in the PS fibers. X-ray diffraction (XRD) spectra of the fibers indicated that the β-CD molecules are distributed within the PS matrix without any phase separated crystalline aggregates up to 40% (w/w) β-CD loading. Furthermore, chemical analyses by Fourier transform infrared (FTIR) spectroscopy studies confirm that β-CD molecules are located within the PS fiber matrix. Finally, preliminary investigations using x-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectrometry (ToF-static-SIMS) show the presence of the cyclodextrin molecules in the outer molecular layers of the fiber surfaces. The XPS and ToF-SIMS findings indicate that cyclodextrin functionalized PS webs would have the potential to be used as molecular filters and/or nanofilters for the purposes of filtration/purification/separation owing to surface associated β-CD molecules which have inclusion complexation capability. © 2009 IOP Publishing Ltd.
Open Access
Liquid crystalline mesophases of pluronics (L64, P65, and P123) and transition metal nitrate salts ([M(H2O)6](NO 3)2)
(American Chemical Society, 2005) Demirörs, A. F.; Eser, B. E.; Dag, Ö.
The triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymers, Pluronics (L64, P65, and P123), form liquid crystalline (LC) mesophases with transition metal nitrate salts (TMS), [M(H2O) n] (NO3)2, in the presence and absence of free water in the media. In this assembly process, M-OH2 plays an important role as observed in a TMS:CnEOm (C nEOm is oligo(ethylene oxide) nonionic surfactants) system. The structure of the LC mesophases and interactions of the metal ion-nitrate ion and metal ion-Pluronic were investigated using microscopy (POM), diffraction (XRD), and spectroscopy (FTIR and micro-Raman) techniques. The TMS:L64 system requires a shear force for mesophase ordering to be observed using X-ray diffraction. However, TMS:P65 and TMS:P123 form well structured LC mesophases. Depending on the salt/Pluronic mole ratio, hexagonal LC mesophases are observed in the TMS:P65 systems and cubic and tetragonal LC mesophases in the TMS:P123 systems. The LC mesophase in the water/salt/Pluronic system is sensitive to the concentration of free (H2O) and coordinated water (M-OH2) molecules and demonstrates structural changes. As the free water is evaporated from the H2O:TMS:Pluronic LC mesophase (ternary mixture), the nitrate ion remains free in the media. However, complete evaporation of the free water molecules enforces the coordination of the nitrate ion to the metal ion in all TMS:Pluronic systems. © 2005 American Chemical Society.
Open Access
Lyotropic liquid-crystalline mesophases of [Zn(H2O)6](NO3)2-C12EO10-CTAB-H2O and [Zn(H2O)6](NO3)2-C12EO10-SDS-H2O systems
(2008) Albayrak, C.; Soylu, A. M.; Dag, Ö.
The mixture of two surfactants (C12EO10-CTAB and C 12EO10-SDS) forms lyotropic liquid-crystalline (LLC) mesophases with [Zn(H2O)6](NO3)2 in the presence of a minimum concentration of 1.75 H2O per C 12EO10. The metal ion/C12EO10 mole ratio can be increased up to 8.0, which is a record high metal ion density in an LLC mesophase. The metal ion concentration can be increased in the medium by increasing the CTAB/C12EO10 or SDS/C12EO 10 mole ratio at the expense of the stability of the LLC mesophase. The structure and some thermal properties of the new mesophase have been investigated using XRD, POM, FTIR, and Raman techniques. © 2008 American Chemical Society.
Open Access
Protein folding rates correlate with heterogeneity of folding mechanism
(American Physical Society, 2004) Öztop, B.; Ejtehadi, M. R.; Plotkin, S. S.
The folding rates of protein were shown to correlate with the degree of heterogeneity in the formation of native contacts. It was shown that both experimental rates and simulated free energy barriers for 2-state proteins depend on the degree of heterogeneity present in the folding process. Heterogeneity due to variance in the distribution of native loop lengths, and variance in the distribution of φ values, were observed to increase folding rates and reduce folding barriers. The observed effect due to φ variance was found to be the most statistically significant, because φ variance captures both heterogeneity arising from native topology and that arising from energetics.
Open Access
A radiotracer study of the adsorption behavior of aqueous Ba2+ ions on nanoparticles of zero-valent iron
(2007) Çelebi O.; Üzüm, C.; Shahwan, T.; Erten H.N.
Recently, iron nanoparticles are increasingly being tested as adsorbents for various types of organic and inorganic pollutants. In this study, nanoparticles of zero-valent iron (NZVI) synthesized under atmospheric conditions were employed for the removal of Ba2+ ions in a concentration range 10-3 to 10-6 M. Throughout the study, 133Ba was used as a tracer to study the effects of time, concentration, and temperature. The obtained data was analyzed using various kinetic models and adsorption isotherms. Pseudo-second-order kinetics and Dubinin-Radushkevich isotherm model provided the best correlation with the obtained data. Observed thermodynamic parameters showed that the process is exothermic and hence enthalpy-driven. © 2007 Elsevier B.V. All rights reserved.
Open Access
Raman studies of doped polycrystalline silicon from laser-annealed, doped a-Si:H
(Pergamon Press, 1994) Compaan, A.; Savage, M. E.; Aydınlı, Atilla; Azfar, T.
We have used Raman scattering to follow the progress of multiple-pulse (sub-melt-threshold) laser annealing in doped hydrogenated amorphous silicon films (a-Si:H) on glass. In phosphorous-doped a-Si:H the Raman signal shows that recrystallization begins with the first laser pulse but the multiple pulses are needed to generate the highest hole concentrations of ∼6×1020 cm-3. In boron-doped a-Si:H the electron concentration reaches ∼1×1021 cm-3 after laser anneal which produces a dip rather than a peak near the phonon line as a consequence of a negative Fano-interference parameter, q. The results show that Raman scattering can be used to obtain carrier concentrations in poly-silicon provided that wavelength-dependent Fano interference effects are properly included. © 1994.
Open Access
Role of organic and inorganic additives on the assembly of CTAB-P123 and the morphology of mesoporous silica particles
(2009) Poyraz, A. S.; Dag, Ö.
Mesoporous silica particles with various morphologies and structures have been synthesized by controlling the solubility, micellization, and assembly of a charged surfactant (cethyltrimethylammonium bromide, CTAB) and a pluronic (PEO20PPO70PEO20, P123) couple using an organic (benzene) or an inorganic (SO4 2-, NO3 -, or Cl-) additive. The effect of CTAB, with or without one of the Hofmeister ions or benzene in various concentrations, on the morphology, pore-size, pore-structure and the nature of the silica particles has been investigated. Increasing the lyotropic anion (SO4 2-) or benzene concentration of the synthesis media creates wormlike particles with enlarged pores and reduced wall thickness. However, the hydrotropic anion (NO3 -) influenced the solubility of the charged surfactant and increased the CTAB concentration in the CTAB-P123 micelles, and as a result, in the mesoporous silica particles. The surface area, unit cell, and pore size of the silica particles are diminished by increasing the nitrate ion centration. The effects of the Cl- ion are between the SO4 2- and NO3 -ions. It influenced the P123 at low and CTAB at high concentrations. At low CTAB/ P123 mol ratios, the Cl- ion affects mainly the P123, but at high CTAB/P123 it affects both the CTAB and P123. By carefully adjusting these ingredients (CTAB, SO4 2-, Cl-, NO3 - and benzene), not only the morphology of the particles, but also the pore-size and pore-structure of the mesoporous silica particles could be adjusted. The investigations were carried out by preparing a series of powder samples and, by varying the CTAB/P123 mol ratio (between 3.0 and 6.0) and the concentration of the organic (0.17 to 0.90 M) or inorganic (at 0.25, 0.50, or 1.00 M) additive in the synthesis media. The powder samples were analyzed using microscopy (SEM, TEM, and POM), diffraction (PXRD), and spectroscopy (FTIR, Raman, UV-vis, and EDS) techniques toward above goals. © 2009 American Chemical Society.