Modeling of a radial-flow moving-bed reactor for dehydrogenation of isobutane

A mathematical model for the performance of a radial-flow moving-bed reactor for dehydrogenation of light paraffins was developed. Assuming relevant kinetic expressions for the main reaction and catalyst deactivation, the kinetic parameters were obtained through lab-scale fixed-bed reactor testing using the integral method of analysis. The conversion was found to be a function of a dimensionless decay time, i.e., the ratio of a “catalyst deactivation time constant” to the residence time of the catalyst within the reactor. For a large dimensionless decay time (negligible catalyst decay), the performance equation approached that of a simple packed-bed reactor. The predictions of the model were compared with those of a commercial unit, and fair agreements were observed.     

Synthesis of 2-mercaptobenzothiazole/magnetic nanoparticles modified multi-walled carbon nanotubes for simultaneous solid-phase microextraction of cadmium and lead

This study describes the successful sequential modification of multi-walled carbon nanotube (MWCNT) by Fe₃O₄ magnetic nanoparticles and 2-mercaptobenzothiazole (MBT) followed by its application as a novel sorbent for simultaneous magnetic solid phase microextraction of lead and cadmium. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to confirm the chemical surface modification of the MWCNT. The ions retained on the 2-MBT/magnetic nanoparticles modified MWCNTs were eluted with 1.0 mL of nitric acid (0.8 mol L^?1) in methanol solution and determined by the flame atomic absorption spectrometry. All parameters affecting the extraction condition were thoroughly investigated and optimised. Under the optimised condition preconcentration factor of 150.0, enhancement factors of 149.0 and 149.2 and limits of detection of 0.21 and 0.01 µg L^?1 were achieved for lead and cadmium, respectively. Using the prepared magnetic nanocomposite, the possible interference of other common ions associated with lead and cadmium determination was effectively avoided and the method was successfully applied to the simultaneous determination of the target ions in various environmental water samples.     

Application of SBA-Pr-SO<Subscript>3</Subscript>H in the synthesis of 2,3-dihydroquinazoline-4(1<Emphasis Type="Italic">H</Emphasis>)-ones: characterization,UV–Vis investigations and DFT studies

An efficient one-pot synthesis of 2,3-dihydroquinazoline-4(1H)-one derivatives 4a–l is described using SBA-Pr-SO₃H as a heterogeneous acid catalyst. The present methodology resulted in various derivatives of 2,3-dihydroquinazoline-4(1H)-one in good yield via a three-component reaction of isatoic anhydride, aldehydes and ammonium acetate. SBA-Pr-SO₃H played a significant role as an efficient mesoporous catalyst due to its pore size of 6 nm. Additionally, UV–Vis spectrum of the products was studied in order to investigate their application as UV absorbers.     

In vivo fluorescent imaging of the mouse retina using adaptive optics

In vivo imaging of the mouse retina using visible and near infrared wavelengths does not achieve diffraction-limited resolution due to wavefront aberrations induced by the eye. Considering the pupil size and axial dimension of the eye, it is expected that unaberrated imaging of the retina would have a transverse resolution of 2 microm. Higher-order aberrations in retinal imaging of human can be compensated for by using adaptive optics. We demonstrate an adaptive optics system for in vivo imaging of fluorescent structures in the retina of a mouse, using a microelectromechanical system membrane mirror and a Shack-Hartmann wavefront sensor that detects fluorescent wavefront.     

Dysprosium pertraction through facilitated supported liquid membrane using D2EHPA as carrier

The pertraction of dysprosium (Dy) through a supported liquid membrane (SLM) system consisting of PTFE (polytetrafluoroethylene) support, D2EHPA (di-2-ethylhexyl phosphoric acid) dissolved in kerosene as membrane solution, and HNO₃ solution as stripping solution, was studied. The experiments were designed by the Taguchi method in order to investigate the effects of initial Dy concentration, feed phase pH, different stripping solution concentration, and D2EHPA concentration in the membrane phase on Dy pertraction. Optimal experimental conditions for Dy pertraction were obtained using an analysis of variance (ANOVA) (feed concentration: 130 mg L^?1, D2EHPA concentration: 0.90 M, feed phase pH: 5, stripping phase concentration: 2 M). In addition, the stability of the carrier in terms of its leaching from the membrane support was studied over a period of 6 days and was found to be satisfactory over that time.     

Effects of ligand tuning on dinuclear indium catalysts for lactide polymerization

Functionalized diaminophenols, H(N(R1R2)N(R3)O), were investigated as ligands for indium catalysts in the ring-opening polymerization of racemic lactide. Precursor complexes (N(Me2)N(Me)O)InCl(2) (1), (N(Pr2)NO)InCl(2) (2), and (N(Mes)NO)InCl(2) (3) were synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Complexes 1 and 2 were used to synthesize alkoxy-bridged complexes [(N(Me2)N(Me)O)InCl](2)(μ-Cl)(μ-OEt) (4) and [(N(Pr2)NO)InCl](2)(μ-Cl)(μ-OEt) (5). These complexes catalysed the polymerization of racemic lactide at different rates, with complex 5 being substantially more active than complex 4. The dissociation behaviour of these catalysts in the presence of lactide was also studied and used to make comparisons with previously reported catalyst systems.     

Preparation and Characterization of Agarose-Gelatin Blend Hydrogels as a Cell Encapsulation Matrix: An In-Vitro Study

Cell encapsulation represents an alternative nonviral technique to treat multiple diseases, leading to a reduction or even absence of administration of immunosuppressants. Hydrogels have been introduced as novel materials suitable for cell encapsulation. This study involves agarose–gelatin blend hydrogels with four different weight percentage ratios (100:0, 75:25, 50:50, 25:75) of agarose to gelatin. Prepared blend hydrogels were assessed in terms of rheological behavior (gel point by using complex viscosity), cell attachment (hemocytometer), cell viability and cytotoxicity (3-(3,4-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliium bromide, MTT assay), and mechanical and integral stability (Bradford test and shear force rupture assay, respectively). Based on the obtained rheological experimental results, the sol-gel transition point for 50:50 was in the physiological condition range (35°C–37°C). The percent of nonattached cells on the surface of the hydrogel decreased from 92% for the 100:0 sample to 46.3% for the 50:50 sample, and the cell viability was more than 95%. A good structural integrity was achieved for samples with weight ratio of 50:50; 20.195% gelatin was released during the 24 h in phosphate buffer solution at 25°C and the mechanical stability of agarose–gelatin microcapsules under shear force were improved about 14% rather than pure agarose microcapsule.     

Observation of transverse Anderson localization in an optical fiber

We utilize transverse Anderson localization as the waveguiding mechanism in optical fibers with random transverse refractive index profiles. Using experiments and numerical simulations, we show that the transverse localization results in an effective propagating beam diameter that is comparable to that of a typical index-guiding optical fiber.     

Preparation of CoSe nanoparticles by microwave-assisted polyol method: effect of Se/Co ratio, support type and synthesis conditions on oxygen reduction activity

Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50?mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH₃/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR.