Band structure and pressure-induced metallic transition in iodine – GW calculation

We have studied the band structure and the band gap closure in phase I of solid iodine under high pressure, using the methods based on the quasiparticle theory, i.e. GW approximation. Our calculations show that the band gap in the Cmca structure, which is the structure of the phase I of solid iodine, closes around 20 GPa. This pressure is near the upper boundary of phase I. We discuss the possible metallic transition in the molecular phase of solid iodine and the possible changes of the crystal structure.     

Discreteness and rationality of F-jumping numbers on singular varieties

We prove that the F-jumping numbers of the test ideal t(X; D, \mathfraka^t){\tau(X; \Delta, \mathfrak{a}^t)} are discrete and rational under the assumptions that X is a normal and F-finite scheme over a field of positive characteristic p, K _X  + Δ is \mathbb Q{\mathbb {Q}}-Cartier of index not divisible p, and either X is essentially of finite type over a field or the sheaf of ideals \mathfraka{\mathfrak{a}} is locally principal. This is the largest generality for which discreteness and rationality are known for the jumping numbers of multiplier ideals in characteristic zero.     

Measurement and analysis of optical gain spectra in 1.6 to 1.8 μm InAs/InP (100) quantum-dot amplifiers

Small signal modal gain measurements have been performed on two-section ridge waveguide InAs/InP (100) quantum-dot amplifiers that we have fabricated with a peak gain wavelength around 1.70 μm. The amplifier structure is suitable for monolithic active-passive integration, and the wavelength region and wide gain bandwidth are of interest for integrated devices in biophotonic applications. A 65 nm blue shift of the peak wavelength in the gain spectrum has been observed with an increase in injection current density from 1,000 to 3,000 A/cm². The quantum-dot amplifier gain spectra have been analyzed using a quantum-dot rate-equation model that considers only the carrier dynamics. The comparison between measured and simulated spectra shows that two effects in the quantum-dot material introduce this large blue shift in the gain spectrum. The first effect is the carrier concentration dependent state filling with carriers of the bound excited and ground states in the dots. The second effect is the decrease in carrier escape time from the dots to the wetting layer with decreasing dot size.     

The RATIO method for time‐resolved Laue crystallography

A RATIO method for analysis of intensity changes in time‐resolved pump–probe Laue diffraction experiments is described. The method eliminates the need for scaling the data with a wavelength curve representing the spectral distribution of the source and removes the effect of possible anisotropic absorption. It does not require relative scaling of series of frames and removes errors due to all but very short term fluctuations in the synchrotron beam.     

Purcell effect of GaAs quantum dots by photonic crystal microcavities

We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.     

The effect of fluorination: a crystallographic and computational study of mesogenic alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates

The series of alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates (F8-n) shows a systematic change of crystal structures depending on the length of the alkyl chain: separate packing of perfluorooctyl (Rf) and alkyl (Rh) chains from each other for shorter (n=2) and longer (n=11) members, alternate packing of Rf and Rh chains for middle (n=6,7) members, and an intermediate type of packing for n=4. Semiempirical MO calculations show slightly repulsive interactions between the Rf chains, and attractive ones between Rf and Rh chains and between Rh and the core of a molecular pair. It is concluded that fluorination determines the molecular shape of the crystal structures by making the chain rigid. It is confirmed that the interactions between Rf chains are small compared with those between other moieties and that they are forced to aggregate owing to the exclusion from other moieties. Thus, the effect is dependent on the geometries and intermolecular interactions of the other moieties.     

An efficient fluorescence sensor for superoxide with an acridinium ion-linked porphyrin triad

Addition of potassium superoxide with 18-crown-6 ether (KO(2)(?-)-18-crown-6) to a toluene solution of an acridinium ion-linked porphyrin triad (Acr(+)-H(2)P-Acr(+)) resulted in a remarkable enhancement of the fluorescence intensity. Thus, Acr(+)-H(2)P-Acr(+) acts as an efficient fluorescence sensor for superoxide. Electron transfer from KO(2)(?-)-18-crown-6 to the Acr(+) moiety to produce the two-electron-reduced species (Acr(?)-H(2)P-Acr(?)) results in inhibition of the fluorescence quenching via photoinduced electron transfer, as revealed by laser flash photolysis measurements.     

Nature of water transport and electro-osmosis in nafion: insights from first-principles molecular dynamics simulations under an electric field

The effects of water content on water transport and electro-osmosis in a representative polymer electrolyte membrane, Nafion, are investigated in detail by means of first-principles molecular dynamics (MD) simulations in the presence of a homogeneous electric field. We have directly evaluated electro-osmotic drag coefficients (the number of water molecules cotransported with proton conduction) from the trajectories of the first-principles MD simulations and also explicitly evaluated factors that contribute to the electro-osmotic drag coefficients. In agreement with previously reported experiments, our calculations show virtually constant values ( approximately 1) of the electro-osmotic drag coefficients for both low and high water content states. Detailed comparisons of each factor contributing to the drag coefficient reveal that an increase in water content increases the occurrence of the Grotthuss-like effective proton transport process, whose contribution results in a decrease in the electro-osmotic drag coefficient. At the same time, an environment that is favorable for the Grotthuss-like effective proton transport process is also favorable for the transport of water arising from water transport occurring beyond the hydration shell around the protons, whose contribution results in an increase in the electro-osmotic drag coefficient. Conversely, an environment that is not favorable for proton conduction is also not favorable for water transport. As a result, the electro-osmotic drag coefficient shows virtually identical values with respect to change in the water content.     

Simultaneous determination of hypoxanthine,inosine, inosine-5′-phosphate and adenosine-5′-phosphate with a multielectrode enzyme sensor

A multielectrode enzyme sensor for the simultaneous determination of adenosine-5′-phosphate (AMP), inosine-5′-phosphate (IMP), inosine (HXR) and hypoxanthine (HX)in fish meat was developed by assembling four enzyme sensors for AMP, IMP, HXR and HX in a flow cell. These compounds were determined from oxygen consumption according to the following reactions: AMP $\text{AD}$ IMP $\text{NT}$ HXR $\text{NP, PO}{}^{\mathrm{3?}}{}_4$ HX $\text{XO, O}{}_2$ Uric acid where AD is AMP deaminase, NT is 5′-nucleotidase, NP is nucleoside phosphorylase and XO is xanthine oxidase. Enzymes were covalently bound to a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. Sensors for HX, HXR, IMP and AMP were prepared by attaching membranes of XO, XONP, XO NPNT, and of XONPNT and AD, respectively, to four oxygen electrodes. Samples extracted from sea bass, bream, flounder, abalone and arkshell were analyzed within 5 min, from the simultaneous response curves of the four electrodes. Results obtained by the multisensor system were in good agreement with those determined by each single electrode.