Sorption kinetics: measurement of surface resistance

Adsorption - The problem of measuring sorption kinetics in microporous adsorbents and distinguishing experimentally between surface resistance and internal diffusion is discussed and reviewed with...     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

The Rectangular Isotherm Model for Adsorption Kinetics

The transient uptake response of an adsorbent particle, subjected to a step change in surface concentration, is considered. It is shown that, when the isotherm is highly favorable, the theoretical curves derived for a Langmuirian system reduce asymptotically to the much simpler form for a rectangular isotherm. The simple rectangular model provides a useful approximation even when the form of the actual isotherm is quite far from the rectangular limit.     

Differential scanning calorimetry and Fourier transform infrared spectroscopic studies of phospholipid organization and lipid-peptide interactions in nanoporous substrate-supported lipid model membranes

High-sensitivity differential scanning calorimetry was utilized to examine whether lipids capable of forming an inverted nonlamellar hexagonal II (HII) phase can be deposited into nanoporous substrate-supported arrays. Particularly, we compare the thermotropic phase properties of nanoconfined unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine lipid bilayers with unsupported dispersions to assess nanoconfinement effects, focusing on the lamellar fluid (Lalpha) to HII phase transition. Experimental results provide direct and clear evidence for the formation of an HII phase upon both heating and cooling. However, a small shift in the Lalpha/HII phase transition temperature, as well as an increase in the magnitude of the associated temperature hysteresis, was observed in the nanoporous substrate-supported system. Additionally, nanoconfinement effects on the interaction and location of the antimicrobial peptide gramicidin S (GS) with nanoporous substrate-supported cardiolipin bilayers were examined by Fourier transform infrared spectroscopy as a function of temperature and phospholipid phase state. Upon heating, GS molecules began to insert into nanoconfined, substrate-supported cardiolipin bilayers at lower temperatures relative to the gel/liquid-crystalline phase transition temperature than into unsupported bilayers. The reduction in the polarity and hydrogen-bonding potential environment of GS in the Lalpha state suggests that GS is located at the polar/apolar interfacial region in both supported and unsupported cardiolipin bilayers and that the capacity of GS to interact with nanoporous substrate-supported cardiolipin bilayers was not significantly hindered by nanoconfinement. These studies further demonstrate the usefulness of supported lipid bilayers inside nanoporous substrates.     

Diffusion of aromatic hydrocarbons in silicalite/HZSM-5

Diffusion of benzene and the xylene isomers in silicalite/HZSM-5 has been studied by a wide range of different experimental techniques. The available data are reviewed in an attempt to draw general conclusions concerning the intracrystalline diffusion process. The results for benzene are remarkably consistent, and the conformity between transport and tracer diffusion and between single crystal membrane and ZLC and frequency response data suggests that diffusion is essentially isotropic with no significant difference between the self and “corrected” transport diffusivity. The situation is more complex for p-xylene which shows clear evidence of non-isotropic behavior and a significant difference between tracer and transport diffusivities.     

Non-planar smoulder propagation governed by diffusion

The steady propagation of a thin smouldering front in a half-spacehas been considered. A suitable coordinate transformation hasallowed the region near the leading edge of the front to beexamined for both a maintained planar surface and with surfacecollapse due to material shrinkage. The change in the oxidizerconcentration for a small increment in the propagation speedfor large time and surface collapse has been determined. Theinfluence of two types of nonlinear diffusion on the shape ofthe smouldering front has been found; other cases can be dealtwith in a similar manner.     

Ultrahigh-sensitivity fiber-optic strain and temperature sensor

We report ultrahigh-sensitivity static strain sensing (noise equivalent strain 相似文献