Dewetting of thin polystyrene films absorbed on epoxy coated substrates

Various characteristics of dewetting of thin polystyrene (PS) films absorbed on highly cross-linked epoxy-coated and silicon oxide covered substrates are studied as a function of PS film thickness (20h(c1) whereas the spinodal dewetting (SD) occurs through the growth of surface undulations for hh(c2) while the SD mechanism is observed for h相似文献   

True nature of active layers in organic solar cells fabricated by sequential casting of donor and acceptor layers

The operation characteristics of nominal bilayer (BL) organic solar cells (OSCs), the active layers (ALs) of which consisted of sequentially casted bottom P3HT donor and top ICBA acceptor layers, resembled those of OSCs with bulk heterojunction (BHJ) ALs. Optical analysis and device simulations showed that such resemblance can be attributed to a similarity in the micromorphology of ALs; as‐deposited BL‐type ALs transformed spontaneously into BHJ‐type ALs. The inclusion of P3HT nanowires (NWs) in the donor layers resulted in different AL micromorphology and consequently a larger power conversion efficiency. Separate assessment of the exciton generation and charge–carrier transport and/or extraction showed that the contribution of P3HT NWs was more prominent in optical effects.

     

Effects of cooling rate and post-heat treatment on properties of ZnO thin films deposited by sol-gel method

Sol-gel spin-coated ZnO thin films are cooled with different rates after the pre-heat treatment. Atomic force microscopy (AFM), X-ray diffraction (XRD), Raman, and photoluminescence (PL) were carried out to investigate the effects of the cooling rate during pre-heat treatment on structural and optical properties of the ZnO thin films. The ZnO thin films cooled slowly exhibit mountain chain structure while the ones cooled rapidly have smooth surface. The ZnO thin films cooled rapidly have higher c-axis orientation compared to the ones cooled slowly. The narrower and the higher near-band-edge emission (NBE) peaks are observed in the ZnO thin films cooled rapidly.     

The quenching of nucleon yields in the nonmesonic weak decay of Λ -hypernuclei and the three-body weak decay process

Recent exclusive coincidence measurements of non-mesonic weak decays (NMWD) reported for the ratio of the partial decay width of neutron-induced-to-proton-induced NMWD, Γ_n/Γ_p , values of 0.45±0.11±0.03 and 0.51±0.13±0.04 for 5lam and ¹² _Λ C , respectively. These observations agree well with the improved theoretical Γ_n/Γ_p ratios which are in the range of 0.3-0.7. It appears that the long-standing discrepancy between the experimental and theoretical values of Γ_n/Γ_p has finally been solved. However, when compared to the results of intra-nuclear cascade (INC) calculations, the observed numbers of both single nucleons and coincident nucleon pairs are strongly quenched. The quenching of the proton yield observed previously has been interpreted as an increase of the Γ_n/Γ_p ratio. On the other hand, significant contributions from the two-nucleon-induced three-body process ΛNN → nNN are predicted. Indeed, the angular correlation of the emitted nucleon pairs in the NMWD of ¹² _Λ C showed not only decay events in back-to-back kinematics, but also events with non-back-to-back kinematics. In this paper we show that the difficulties to extract the correct Γ_n/Γ_p ratio from the proton spectra is related to the three-body weak-interaction process which strongly quenches the nucleon yields.     

Study of the interfacial structure in epoxy bilayer films using neutron reflection

The interfacial structure in thin epoxy bilayer films was investigated with neutron reflection. For each experiment, a mixture of crosslinker and deuterated resin was spun onto a chemically similar, fully cured, protonated epoxy film. The reflectivity measurements were performed before and after curing the top epoxy film. We focused on the extent of penetration of the components of the top layer into the network of the bottom layer. The effect of the cure temperature of each layer was examined. In addition, the effect of the initial molecular weight of the oligomers in the top layer was probed by the partial curing of the mixture before spinning. As deposited, the components of the top layer penetrated the bottom layer to an extent that was largely independent of the aforementioned factors. The principal observation was that an additional penetration occurred with curing. This additional penetration was dependent upon both the molecular weight of the top layer and the cure temperature of the top layer relative to the glass‐transition temperature of the bottom layer. A decrease in the thickness of the top layer with curing was also observed, which likely indicates some evaporation of oligomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1709–1718, 2002     

A novel iridoid from Boschniakia rossica

A novel iridoid, (4R)-4-hydroxymethylboschnialactone (1), has been isolated from Boschniakia rossica, together with three previously known compounds, (24S)-3beta-hydroxy-24-ethylcholest-5-en-7-one (2), (24R)-3beta-hydroxy-24-ethylcholest-5-en-7-one (3) and methyl p-coumarate, using column chromatography. The structures of compounds were elucidated by spectroscopic methods.     

EPR spectra and structure of the chlorotrifluoroethylene and bromotrifluoroethylene radical anions

EPR spectra attributable to the halogenotrifluoroethylene radical anions have been generated by electron attachment in solid solutions at low temperatures. The spin density distribution in these radicals strongly suggests that the unpaired electron occupies a σ^* orbital, a conclusion which is supported by CNDO/2 calculations.     

Applicability of X-ray microscopy to non-contact tablet mass estimation

The pharmaceutical tablet manufacturing process requires a tablet mass measuring step to ensure that all tablets have the prescribed dosage. The digital scales commonly used for that purpose require tens of seconds to stabilize, resulting in a substantial slow-down of the manufacturing process. The alternative visual approaches are fallible because of the potential existence of voids and cracks in the tablets. This paper uses an X-ray microscopy for mass measurement. Albeit with some constraints concerning tablet size and constituents, the approach can measure a tablet’s mass in under one second, and may constitute, in the future, a viable and practical approach.     

Highly active and stable DNAzyme-carbon nanotube hybrids

We report herein the generation and characterization of DNAzyme-carbon nanotube conjugates. Biotinylated DNAzyme was attached to streptavidin-functionalized MWNTs. The resultant DNAzyme-MWNT conjugates exhibited Michaelis-Menten kinetics and multiple catalytic turnovers. The specific activity of the nanoscale conjugates was approximately 1/3 of that for freely soluble DNAzyme. Such high activity may allow myriad applications ranging from the directed assembly of nanomaterials to nanoscale cellular therapeutics that rely on the RNA cleaving ability of DNAzymes.