rGO Sheets/ZnFe2O4 Nanocomposities as an Efficient Electro Catalyst Material for I3−/I− Reaction for High Performance DSSCs

In this paper, Reduced Graphene Oxide (rGO)/ZnFe₂O₄ (rZnF) nanocomposite is synthesized by a simple hydrothermal method and employed as a counter electrode (CE) material for tri-iodide redox reactions in Dye sensitized solar cells (DSSC) to replace the traditional high cost platinum (Pt) CE. X-ray diffraction analysis and High resolution Transmission electron microscopy, clearly indicated the formation of rZnF nanocomposite and also amorphous rGO sheets were smoothly distributed on the surface of ZnFe₂O₄ (ZnF) nanostructure. The rZnF-50 CE shows excellent electro catalytic activity toward I₃^? reduction, which has simultaneously been confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization measurements. A DSSC developed by rZnF-50 CE (η?=?8.71%) obtained quite higher than the Pt (η?=?8.53%) based CE under the same condition. The superior performances of rZnF-50 CE due to addition of graphene in to Spinel (ZnF) nanostructure results in creation of highly active electrochemical sites, fast electron transport linkage between CE and electrolyte. Thus it’s a promising low cost CE material for DSSCs.

     

Leucine enkephalin—A mass spectrometry standard

The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of leucine enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry‐related information on leucine enkephalin has been critically reviewed and summarized. The fragmentation mechanism of leucine enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, leucine enkephalin is often used as a thermometer molecule in electrospray or matrix‐assisted laser desorption ionization (ESI or MALDI). Other parameters described for leucine enkephalin include collisional cross‐section and energy transfer; proton affinity and gas‐phase basicity; radiative cooling rate; and vibrational frequencies. The lowest‐energy fragmentation channel of leucine enkephalin is the MH⁺ → b₄ process. All available data for this process have been re‐evaluated. It was found that, although the published E_a values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature‐ and energy‐dependent rate constants were re‐evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R² = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 10^11.0 sec^?1 pre‐exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10^±0.5 sec^?1, respectively. The activation entropy at 470 K that corresponds to this reaction is ?38.1 ± 9.6 J mol^?1 K^?1. We believe that these re‐evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as “consensus” values; results on other processes might be compared to this reference value. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:298–320, 2011     

Reliability assessment of 3D space frame structures applying stochastic finite element analysis

Throughout design development of satellite structure, stress engineer is usually challenged with randomness in applied loads and material properties. To overcome such problem, a risk-based design is applied which estimates satellite structure probability of failure under static and thermal loads. Determining probability of failure can help to update initially applied factors of safety that were used during structure preliminary design phase. These factors of safety are related to the satellite mission objective. Sensitivity-based analysis is to be implemented in the context of finite element analysis (probabilistic finite element method or stochastic finite element method (SFEM)) to determine the probability of failure for satellite structure or one of its components.     

Low-Temperature Processing of PZT Thick Film by Seeding and High-Energy Ball Milling and Studies on Electrical Properties

Lead zirconate titanate thick film with molecular formula PbZr_0.52Ti_0.42O₃ (PZT) was prepared by a modified conventional sol–gel method through seeding and high-energy ball milling, resulting in perovskite phase formation at lower temperatures. The ball-milling time was optimized by keeping the seed particle loading (5 wt.%) constant in the sol–gel solution. This methodology helped in reduction of the crystalline phase formation temperature to 300°C, which is much lower than that reported in the literature (450°C). The well-established perovskite phase was confirmed by x-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) of PZT films revealed uniform and crystalline microstructure. Film prepared by this methodology showed higher spontaneous polarization (2.22 μC/cm²), higher capacitance (1.17 nF), and low leakage current density (18 μA/cm²). The results obtained from ferroelectric characterization showed a strong correlation with the XRD and SEM results.     

Ultraviolet light effect on electrical properties of a flexible organic thin film transistor

We have fabricated pentacene-based transistors on a transparent and flexible substrate made of polyethylene-terephthalate. We have shown that using an optical excitation at a wavelength of 365 nm photoconductivity modifies the carrier density without changing the mobility. The performance of the flexible organic phototransistors is mostly due to high-photosensitivity in the off-state with a ratio of photocurrent to dark current of about 2 10⁴. Furthermore, the response times of the phototransistor are lower than 0.1 s. These results indicate that such transistors could be potentially used in photodetectors or amplifiers ordered by an optical gate. Moreover, we have noticed that there is no significant change in the mobility value when the transistor is bent in the direction of the current flow.     

Representation and extrapolation in multilayer perceptrons

To give an adequate explanation of cognition and perform certain practical tasks, connectionist systems must be able to extrapolate. This work explores the relationship between input representation and extrapolation, using simulations of multilayer perceptrons trained to model the identity function. It has been discovered that representation has a marked effect on extrapolation.     

Domain organization of the extracellular region of CD45

CD45 is a large, heavily glycosylated, transmembrane proteinphosphotyrosine phosphatase found on all nucleated cells ofhaematopoietic origin. In lymphocytes, the cytoplasmic phosphataseis necessary for efficient signalling through the antigen receptorbut in contrast little is known about the interactions of theextracellular region of the molecule. This consists of a mucin-likeregion, a novel cysteine-containing region and a region containingthree putative fibronectin type III domains. To confirm thisorganization and to identify parts potentially important forfunction, we have expressed fragments of the extracellular domainof rat CD45 as recombinant soluble proteins. Proteins correspondingto two, three and four domains of CD45 were expressed in secretedforms. Single domains and constructs for proteins with truncationsof the predicted domains were not expressed. This is consistentwith the proposed structural organization. Determination ofthe positions of the disulphide bonds in the N-terminal cysteine-containingregion and the first fibronectin type III domain identifiednovel disulphide bonds within the fibronectin type III domainand an unusual inter-domain disulphide linkage. Circular dichroismspectroscopy indicated that this region of rat CD45 has mainlyß-strand secondary structure and no -helical content.These studies support the proposed domain organization of CD45.