Nanostructure evolution in high-temperature perfluorosulfonic acid ionomer membrane by small-angle X-ray scattering

The high-temperature morphology of supported liquid membranes (SLMs) prepared from perfluorinated membranes such as Nafion and Hyflon and hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-TFSI) has been investigated by small-angle X-ray scattering (SAXS). Proton conductivity results of SLMs before and after leaching show an increase in conductivity with temperature up to 160 °C in an anhydrous environment. DSC results show that crystallites within perfluorinated membranes are thermally stable up to 196 °C. High-temperature SAXS results have been used to correlate structure and morphology of supported liquid membranes with high-temperature conductivity data. The ionic liquid essentially acts as a proton solvent in a similar way to water in hydrated Nafion membranes and increases size of clusters, which allow percolation to be achieved more easily. The cation of the ionic liquid interacts with sulfonate groups within ionic domains through electrostatic interactions and displaces protons. Protons can associate with free anions of the ionic liquid, which are loosely associated with cations and can transport by hopping from anion sites within the membrane. The ionic liquid contributes to proton conductivity at high temperature through achievement of long-range ordering and subsequent percolation.     

Characteristic and non-characteristic X-ray yields produced from thick Ti element by sub-relativistic electrons

Measurements are performed to study the electron impact energy dependence of doubly differential bremsstrahlung yields (DDBY) and of characteristic Ti K_α line yields produced from sub-relativistic electrons (10–25 keV) colliding with a thick Ti (Z = 22) target. The emitted radiation is detected by a Si-PIN photo-diode detector with energy resolution (FWHM) of 180 eV at 5.9 keV. The measured data of DDBY are compared with the results predicted by Monte-Carlo (MC) simulations using the general purpose PENELOPE code. A reasonable agreement is found between experimental and simulation results within the experimental uncertainty of measurements of 12%. Characteristic Ti K_α yields are obtained for the considered impact energy range and they are compared with the existing theoretical results. A good agreement is found between the present measurements and the theoretical calculations. Furthermore, data are presented for impact energy dependence of the ratio K_α/(K_α+ K_β) of a thick Ti target under impact of 10–25 keV electrons. The ratio shows a very weak dependence on impact energy in the studied range. The average value of the ratio is found to be 0.881 ± 0.003.     

Magnetic field modulation spectroscopy of rubidium atoms

The magnetically modulated saturation absorption profile is studied for a wide range of external DC magnetic field. The salient features of Doppler-free signal generated by laser frequency modulation and atomic energy level modulation are compared. The DC offset of the signal profile is found to be unstable as the external DC magnetic field is changed. The technical difficulty of tuning laser frequency under locked condition over a large frequency span is discussed along with possible solutions.     

25-原子金纳米球和纳米棒催化性能的比较(英文)

The catalytic properties of two nanocluster catalysts with atomically precisely known structures,icosahedral two-shelled Au25(SC2H4Ph) 18 nanospheres and biicosahedral Au25(PPh3) 10(SC2H4Ph) 5Cl2 nanorods,were compared. Their catalytic performance in the two reactions of the selective oxidation of styrene and chemoselective hydrogenation of α,β-unsaturated benzalacetone was investigated. The catalytic activities of icosahedral Au25(SC2H4Ph) 18 nanospheres were superior to those of the bi-icosahedral Au25(PP...     

Mechanism and kinetics of the isothermal thermodegradation of ethylene-propylene-diene (EPDM) elastomers

The thermal degradation behavior of a range of ethylene-propylene-diene (EPDM) elastomers, covering the whole range of composition, has been examined under isothermal conditions between 410 and 440 °C using thermogravimetric analysis. The kinetic parameters of degradation for the polymers have been evaluated using different mathematical models based on different proposed mechanisms of degradation. The experimental data were fitted to the models using non-linear regression analysis technique based on Marquardt-Levenberg algorithm. It appears that the degradation of EPDMs follows the Avrami-Erofeev two-dimensional nucleation model or a random chain-scission mechanism. No observable trend was found between the ethylene content of EPDM and the activation energy of degradation.     

Self-acylation properties of type II fatty acid biosynthesis acyl carrier protein

Acyl carrier protein (ACP) plays a central role in many metabolic processes inside the cell, and almost 4% of the total enzymes inside the cell require it as a cofactor. Here, we report self-acylation properties in ACPs from Plasmodium falciparum and Brassica napus that are essential components of type II fatty acid biosynthesis (FAS II), disproving the existing notion that this phenomenon is restricted only to ACPs involved in polyketide biosynthesis. We also provide strong evidence to suggest that catalytic self-acylation is intrinsic to the individual ACP. Mutational analysis of these ACPs revealed the key residue(s) involved in this phenomenon. We also demonstrate that these FAS II ACPs exhibit a high degree of selectivity for self-acylation employing only dicarboxylic acids as substrates. A plausible mechanism for the self-acylation reaction is also proposed.     

An Efficient Probe for Rapid Detection of Cyanide in Water at Parts per Billion Levels and Naked‐Eye Detection of Endogenous Cyanide

A new molecular probe based on an oxidized bis‐indolyl skeleton has been developed for rapid and sensitive visual detection of cyanide ions in water and also for the detection of endogenously bound cyanide. The probe allows the “naked‐eye” detection of cyanide ions in water with a visual color change from red to yellow (Δλ_max=80 nm) with the immediate addition of the probe. It shows high selectivity towards the cyanide ion without any interference from other anions. The detection of cyanide by the probe is ratiometric, thus making the detection quantitative. A Michael‐type addition reaction of the probe with the cyanide ion takes place during this chemodosimetric process. In water, the detection limit was found to be at the parts per million level, which improved drastically when a neutral micellar medium was employed, and it showed a parts‐per‐billion‐level detection, which is even 25‐fold lower than the permitted limits of cyanide in water. The probe could also efficiently detect the endogenously bound cyanide in cassava (a staple food) with a clear visual color change without requiring any sample pretreatment and/or any special reaction conditions such as pH or temperature. Thus the probe could serve as a practical naked‐eye probe for “in‐field” experiments without requiring any sophisticated instruments.     

Einstein–Podolski–Rosen paradox,non-commuting operator,complete wavefunction and entanglement

Einstein, Podolski and Rosen (EPR) have shown that any wavefunction (subject to the Schrödinger equation) can describe the physical reality completely, and any two observables associated with two non-commuting operators can have simultaneous reality. In contrast, quantum theory claims that the wavefunction can capture the physical reality completely, and the physical quantities associated with two non-commuting operators cannot have simultaneous reality. The above contradiction is known as the EPR paradox. Here, we unambiguously expose that there is a hidden assumption made by EPR, which gives rise to this famous paradox. Putting the assumption right this time leads us not to the paradox, but only reinforces the correctness of the quantum theory. However, it is shown here that the entanglement phenomenon between two physically separated particles (they were entangled prior to separation) can only be proven to exist with a ‘proper’ measurement.     

Monitoring Local pH of Membranous Aggregates via Ratiometric Color Changing Response

A series of oxidized di(indolyl)arylmethanes (DIAM) with polyaromatic signaling moieties have been designed for monitoring local pH at the interfacial region of surfactant aggregates, such as micelles and vesicles. The oxidized DIAMs show changes in solution color from red to yellow when incorporated in cationic surfactants (at pH 7.4) and yellow to reddish pink when exposed to negatively-charged surfactants (at pH 5.0). The changes in surface charge can influence the interfacial pH (distinct from bulk pH of the medium) of the surfactant aggregates. The mechanistic studies indicate that the red-shifted absorption maxima observed in the presence of anionic amphiphiles (acidic local pH) originated from the protonated species. On the contrary, maxima in the blue region, triggered by positively charged amphiphiles (basic local pH), is attributed to the zwitterionic species. Such prototropic equilibrium affects charge transfer states of the molecules along with their self-assembly properties. Thus, it is evident that probes can predict as well as quantify the local pH change using the pseudophase ion exchange formalism. Also, the probes can detect the presence of anionic amphiphiles even when bound to phospholipid membranes.