Nonlocal density functional calculation of gas phase heats of formation

A general procedure is presented for computing the gas phase heats of formation of a wide variety of organic compounds. ΔE for the formation of the molecule from its elements at 0 K is obtained from density functional calculations (Gaussian 92/DFT) for optimized geometries. This result is converted to ΔH at 298 K by assuming ideal behavior and adding the translational, rotational, and vibrational energies. Additive correction terms corresponding to the various coordination states of the carbons, nitrogens, and oxygens were developed using a database of 54 compounds. The experimental ΔH values of these compounds are then reproduced with an average absolute error of 3 kcal/mol and a standard deviation of 4 kcal/mol. For a group of 10 test cases that were not part of the database, the average absolute error is 3.5 kcal/mol and the standard deviation is 4.1 kcal/mol. © 1995 by John Wiley & Sons, Inc.     

Comparison of Artificial Neural Networks with Partial Least Squares Regression for Simultaneous Determinations by ICP-AES

Simultaneous determination of several elements （U, Ta, Mn, Zr and W） with inductively coupled plasma atomic emission spectrometry （ICP-AES） in the presence of spectral interference was performed using chemometrics methods. True comparison between artificial neural network （ANN） and partial least squares regression （PLS） for simultaneous determination in different degrees of overlap was investigated. The emission spectra were recorded at uranium analytical line （263.553 nm） with a 0.06 nm spectral window by ICP-AES. Principal component analysis was applied to data and scores on 5 dominant principal components were subjected to ANN. A 5-5-5 （input, hidden and output neurons） network was used with linear transfer function after both hidden and output layers. The PI,S model was trained with five latent variables and 20 samples in calibration set. The relative errors of predictions （REP） in test set were 3.75% and 3.56% for ANN and PLS respectively.     

Lp ‐estimates for the Bergman projection on strictly pseudoconvex nonsmooth domains

We consider the Bergman projection on Henkin–Leiterer domains, bounded strictly pseudoconvex domains which have defining functions whose gradient is allowed to vanish. Our result describes the mapping properties of the Bergman projection between weighted L^p spaces, with the weights being powers of the gradient of the defining function. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluating the electrochemical properties of PEO‐based nanofibrous electrolytes incorporated with TiO2 nanofiller applicable in lithium‐ion batteries

In the present work, nanofibrous composite polymer electrolytes consist of polyethylene oxide (PEO), ethylene carbonate (EC), propylene carbonate (PC), lithium perchlorate (LiClO₄), and titanium dioxide (TiO₂) were designed using response surface method (RSM) and synthesized via an electrospinning process. Morphological properties of the as‐prepared electrolytes were studied using SEM. FTIR spectroscopy was conducted to investigate the interaction between the components of the composites. The highest room temperature ionic conductivity of 0.085 mS.cm^?1 was obtained with incorporation of 0.175 wt. % TiO₂ filler into the plasticized nanofibrous electrolyte by EC. Moreover, the optimum structure was compared with a film polymeric electrolyte prepared using a film casting method. Despite more amorphous structure of the film electrolyte, the nanofibrous electrolyte showed superior ion conductivity possibly due to the highly porous structure of the nanofibrous membranes. Furthermore, the mechanical properties illustrated slight deterioration with incorporation of the TiO₂ nanoparticles into the electrospun electrolytes. This investigation indicated the great potential of the electrospun structures as all‐solid‐state polymeric electrolytes applicable in lithium ion batteries.     

An investigation on polycaprolactone/chitosan/Fe3O4 nanofibrous composite used for hyperthermia

Hyperthermia is considered as an effective supplementary cancer treatment. However, the uneven temperature distribution is the major challenge in hyperthermia. Nanotechnology could solve this problem by applying magnetic nanoparticles directly or in nanofibers as implants. Low solubility, poor cancer targeting, and leakage are limitations of free magnetic nanoparticles. In this work, Fe₃O₄ nanoparticles were loaded into polycaprolactone/chitosan blended nanofibers in various contents. Magnetic, chemical, physical, and morphology of the derived nanofibrous composites were then studied. The results showed the magnetic properties of the nanocomposite had low coercivity, which was close to superparamagnetic particles. Chemical analysis showed that components had no interaction with each other. Nevertheless, Fe₃O₄ was slightly transformed to other iron oxides. However, the magnetic analysis showed this transformation had no significant effect on final magnetic content of the nanofibers. The results of X‐ray diffraction (XRD) (19.5 nm), transmittance electron microscopy (TEM) (21.6 nm), and vibration sample magnetometer (VSM) (17 nm) suggested that the magnetic nanoparticles were single domain. Thermal analysis results showed that 7% Fe₃O₄ nanofibers had more heat increase as oppose to other nanofibrous composites in the alternative magnetic field (AMF). Nonetheless, the heat performance of 3% Fe₃O₄ nanofibers was more than others according to its specific power absorption (SPA). Therefore, due to the importance of using nanoparticles in the least possible content, this method can be used as a postsurgical treatment by applying these nanofibrous composites as implants on the tumor site. Moreover, these nanofiber composites could carry anticancer drugs, which are applied as a multi‐mode treatment system.     

Synthesis and characterization of a novel polyurethane/polypyrrole‐p‐toluenesulfonate (PU/PPy‐pTS) electroactive nanofibrous bending actuator

Electroactive actuators based on conductive polymers currently have attracted a great deal of attention. In this study, a nanofibrous structure of polypyrrole (PPy) was used to fabricate an electroactive bending actuator. For this purpose, polyurethane/PPy (PU/PPy) nanofibrous bending actuator was fabricated through the combined use of electrospinning and in‐situ chemical polymerization. The response surface methodology (RSM) was considered to find the optimal electrospinning conditions for producing PU nanofibers with the minimum diameter. The in‐situ chemical polymerization method was then used to prepare a conductive layer of PPy on the surface of optimum electrospun nanofibers with p‐toluenesulfonate (pTS) as the dopant. The coated nanofibers were used in the fabrication of PU/PPy‐pTS nanofibrous bending actuator. The morphology and electrical, thermal, electrochemical, and electrochemomechanical properties of the fabricated actuator were investigated. By using optimum conditions of electrospinning, PU nanofibers were obtained with a diameter of 221 nm. The results showed that the produced PU/PPy‐pTS nanofibers enjoy good thermal stability and have an electrical conductivity of about 276.34 S/cm. The obtained cyclic voltammetric and dynamo‐voltammetric responses showed that the dominant mechanism of actuation in the fabricated PU/PPy‐pTS nanofibrous actuator is the exchange of perchlorate anions with a partial exchange of lithium cations in 1M lithium perchlorate electrolyte solution. The fabricated actuator was capable of undergoing 141° reversible angular displacement during a potential cycle. The results demonstrated that, given high porosity, large specific surface area, flexibility, and desirable electrical properties, PU/PPy nanofibrous electroactive actuator provides a lot of potential for developing artificial muscle applications.     

Inhomogeneous metallic phase in a disordered Mott insulator in two dimensions

We show that, with increasing randomness, the spectral gap in a 2D Mott-Hubbard insulator is destroyed first at a disorder V(c1), while antiferromagnetism persists up to a higher V(c2). Most unexpectedly, between V(c1) and V(c2) the system is metallic and is sandwiched between the Mott insulator below V(c1) and the Anderson insulator above V(c2). The metal is formed when the spectral gap gets destroyed locally in regions where the disorder potential is high enough to overcome the interelectron repulsion. This generates puddles with enhanced charge fluctuations that percolate with increasing disorder, resulting in a spatially inhomogeneous metallic phase.