Kinetic and mechanistic modeling of acid‐catalyzed degradation of polymers with various cracking catalysts

A new approach is presented that combines kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation in the modeling of the catalytic degradation of polymers. Though acid‐catalyzed hydrocarbon cracking reactions involve a large number of compounds, reactions and catalyst deactivation and are very complex, the model gives a good representation of experimental results from the degradation of polyethylene and polypropylene over fluidized acidic catalysts. This model provides the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics, and coke in relation to the effect of structurally different polymer feeds, the performance of the catalyst and the selection of their particle sizes, and the influence of different reaction temperatures. It is an improvement of the currently available empirical “lumping” techniques which usually are severely restricted in terms of product definitions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Finite-Element Simulations of Full-Scale Modular-Block Reinforced Soil Retaining Walls under Earthquake Loading

A finite-element procedure was used to simulate the dynamic behavior of four full-scale reinforced soil retaining walls subjected to earthquake loading. The experiments were conducted at a maximum horizontal acceleration of over 0.8 g, with two walls subjected to only horizontal accelerations and two other walls under simultaneous horizontal and vertical accelerations. The analyzes were conducted using advanced soil and geosynthetic models that were capable of simulating behavior under both monotonic and cyclic loadings. The soil behavior was modeled using a unified general plasticity model, which was developed based on the critical state concept and that considered the stress level effects over a wide range of densities using a single set of parameters. The geosynthetic model was based on the bounding surface concept and it considered the S-shape load-strain behavior of polymeric geogrids. In this paper, the calibrations of the models and details of finite-element analysis are presented. The time response of horizontal and vertical accelerations obtained from the analyses, as well as wall deformations and tensile force in geogrids, were compared with the experimental results. The comparisons showed that the finite-element results rendered satisfactory agreement with the shake table test results.     

Attraction of semiconductor nanowires: An in situ observation

In situ deformation transmission electron microscopy was used to study the attraction behavior of GaAs semiconductor nanowires (NWs). The NWs demonstrated an interesting phenomenon of either head-to-head or body-to-body attraction at distances that depend on the NW diameters. The NWs with a diameter of ～25 nm attracted at a distance of ～25 nm, while large-diameter NWs of ～55 nm showed no obvious attraction. The underlying mechanism governing the attraction of the NWs is proposed and discussed with a mechanistic model. The diameter dependence on the NW attraction behavior is discussed. The finding provides an understanding of the Ampère force in nanostructured materials caused by an electron-beam-induced current while technologically it provides useful hints for designing NW-based devices according to the diameter-dependent attraction behavior of NWs.     

Effects of crystallization behavior on morphological change in poly(trimethylene terephthalate) spherulites

In poly(trimethylene terephthalate) (PTT) spherulites during isothermal crystallization, the morphological changed from an axialite/or elliptical banded spherulite to banded spherulite and then non-banded spherulite with temperature decreasing were studied by following the lamellar growth behaviors. We report lamellar growth mechanism on varied crystallization temperature, which explicitly probes the link between microscopic structure and macroscopic morphology in the development of patterns. Fibrillation of the edge-on lamellae was observed on the surfaces of axialite and the convex bands of banded spherulite. Terrace-like lamellae were observed on the surface of the non-banded spherulite and the concave bands of banded-spherulite. In thin film crystallization, PTT banded spherulite exhibits a texture of alternate edge-on and flat-on lamellae, wavy-like surface and rhythmic growth. The deceleration of growth rate takes place in convex bands with a growth habit of fibrillation of the edge-on lamellae for emerging ridge surface. On the other hand, the acceleration of growth rate appears in concave bands with a growth habit of terrace-like lamellae for emerging valley surface. The alternating growth mechanism of the lamellae was considered to be related with the formation of spatiotemporal self-organization patterns far from equilibrium. In order to explain the rhythmic growth and periodic growth of the lamellae, we may conjecture that the emergence of PTT banded spherulite in thin film crystallization is associated with an oscillatory dynamics of the spherulite growth front driven by latent heat diffusion. We present some tentative ideas on the possibility of band-to-nonband (BNB) morphological transition, which might be analogous with the second order transition in non-equilibrium phase transition.     

Silicon–Carbon Stressors With High Substitutional Carbon Concentration and In Situ Doping Formed in Source/Drain Extensions of n-Channel Transistors

We report the first demonstration of n-channel field-effect transistors (N-FETs) with in situ phosphorus-doped silicon-carbon (SiCP) stressors incorporated in the source/drain extension (SDE) regions. A novel process which formed recessed SDE regions followed by selective epitaxy of SiCP was adopted. High in situ doping contributes to low series resistance to channel resistance ratio and is important for reaping the benefits of strain. Substitutional carbon concentration was varied, showing enhanced drive current with increased for comparable off-state leakage, series resistance, and control of short-channel effects. A record high carbon substitutional concentration of 2.1% was achieved. Use of heavily doped silicon-carbon stressor with large lattice mismatch with respect to Si and placed in close proximity to the channel region in the SDE regions is expected to be important for strain engineering in nanoscale N-FETs.     

Microstructure and Tensile Properties of Sn-1Ag-0.5Cu Solder Alloy Bearing Al for Electronics Applications

This work investigates the effects of 0.1?wt.% and 0.5?wt.% Al additions on bulk alloy microstructure and tensile properties as well as on the thermal behavior of Sn-1Ag-0.5Cu (SAC105) lead-free solder alloy. The addition of 0.1?wt.% Al reduces the amount of Ag₃Sn intermetallic compound (IMC) particles and leads to the formation of larger ternary Sn-Ag-Al IMC particles. However, the addition of 0.5?wt.% Al suppresses the formation of Ag₃Sn IMC particles and leads to a large amount of fine Al-Ag IMC particles. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions suppress the formation of Cu₆Sn₅ IMC particles and lead to the formation of larger Al-Cu IMC particles. The 0.1?wt.% Al-added solder shows a microstructure with coarse ??-Sn dendrites. However, the addition of 0.5?wt.% Al has a great effect on suppressing the undercooling and refinement of the ??-Sn dendrites. In addition to coarse ??-Sn dendrites, the formation of large Sn-Ag-Al and Al-Cu IMC particles significantly reduces the elastic modulus and yield strength for the SAC105 alloy containing 0.1?wt.% Al. On the other hand, the fine ??-Sn dendrite and the second-phase dispersion strengthening mechanism through the formation of fine Al-Ag IMC particles significantly increases the elastic modulus and yield strength of the SAC105 alloy containing 0.5?wt.% Al. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions worsen the elongation. However, the reduction in elongation is much stronger, and brittle fracture occurs instead of ductile fracture, with 0.5?wt.% Al addition. The two additions of Al increase both solidus and liquidus temperatures. With 0.5?wt.% Al addition the pasty range is significantly reduced and the differential scanning calorimetry (DSC) endotherm curve gradually shifts from a dual to a single endothermic peak.     

The validity of self-reported seatbelt use in a country where levels of use are low

The validity of self-reported seatbelt use among low belt use populations in low belt use countries has not been evaluated directly. Nine hundred and ninety drivers were recruited from shopping centers, car parks, and other suitable locations located in Afyon and Ankara cities of Turkey in order to compare the self-reported and observed seatbelt usage rates. Data sets were collected simultaneously from the participants not being aware of having their seatbelt use observed. Participants interviewed in Afyon (n = 301) and Ankara (n = 658) reported seatbelt usage (“always using a seatbelt”) rates of 39% and 45%, respectively. When observed, however, only 47% in Afyon and 70% in Ankara of these drivers actually fasten their seat-belts. It seems that the drivers in both cities exaggerated their use seat belts considerably.     

Identification of low-abundance cancer biomarker candidate TIMP1 from serum with lectin fractionation and peptide affinity enrichment by ultrahigh-resolution mass spectrometry

As investigating a proteolytic target peptide originating from the tissue inhibitor of metalloproteinase 1 (TIMP1) known to be aberrantly glycosylated in patients with colorectal cancer (CRC), we first confirmed that TIMP1 is to be a CRC biomarker candidate in human serum. For this, we utilized matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) showing ultrahigh-resolution and high mass accuracy. This investigation used phytohemagglutinin-L(4) (L-PHA) lectin, which shows binding affinity to the β-1,6-N-acetylglucosamine moiety of N-linked glycan on a protein, to compare fractionated aberrant protein glycoforms from both noncancerous control and CRC serum. Each lectin-captured fraction containing aberrant glycoforms of TIMP1 was digested by trypsin, resulting in the tryptic target peptide, representative of the serum glycoprotein TIMP1. The resulting target peptide was enriched using a stable isotope standard and capture by the antipeptide antibody (SISCAPA) technique and analyzed by a 15 T MALDI FTICR mass spectrometer with high mass accuracy (Δ < 0.5 ppm to the theoretical mass value of the target peptide). Since exact measurement of multiplex isotopic peaks of the target peptide could be accomplished by virtue of high mass resolution (Rs > 400,000), robust identification of the target peptide is only achievable with 15 T FTICR MS. Also, MALDI data obtained in this study showed that the L-PHA-captured glycoforms of TIMP1 were measured in the pooled CRC serum with about 5 times higher abundance than that in the noncancerous serum, and were further proved by MRM mass analysis. These results confirm that TIMP1 in human serum is a potent CRC biomarker candidate, demonstrating that ultrahigh-resolution MS can be a powerful tool toward identifying and verifying potential protein biomarker candidates.     

Synthesis of fluorene-based semiconducting copolymers for organic solar cells

Semiconducting polymers composed of 2,2'-(9,9-dioctyl-9H-fluorene-2,7-diyl)dithiophenes (F8T2s) and (2E,2'E)-3,3'-(2,5-bis(octyloxy)-1,4-phenylene) bis(2-(5-bromothiophene-2-yl)acrylonitrile)s (OPTANs) have been synthesized through Pd(O)-catalyzed Suzuki coupling polymerization by controlling the monomer ratio. The synthesized polymers were confirmed to exhibit good solubility in common solvents, simple processability, and thermal stability up to 350 degrees C. The highest occupied molecular orbitals (HOMOs), lowest unoccupied molecular orbitals (LUMOs), and optical band-gap energies were determined using cyclic voltammetry (CV) and UV-visible spectrometry. The synthesized polymers showed their maximum absorption and edge at around 520 and 650 nm, respectively. The optical band-gap energies of the polymers were determined to be 1.89 eV. Bulk heterojunction organic solar cells were fabricated using the conjugated polymer as the electron donor, and 6,6-phenyl C61-butyric acid methylester (PC61BM) or 6,6-phenyl C71-butyric acid methylester (PC71BM) as the electron acceptor. The power conversion efficiencies (PCEs) of the solar cells based on polymer:PC71BM (1:1) and polymer:PC71BM (1:2) were 0.68% and 1.22%, respectively, under air mass 1.5 global (AM 1.5 G) illumination at 100 mW/cm2.