Positive parity states and some electromagnetic transition properties of even-odd europium isotopes

The positive-parity low-spin states of even-odd Europium isotopes (^151–155Eu) were studied within the framework of the interacting boson-fermion model. The calculated positive low-spin state energy spectra of the odd Eu isotope were found to agree quite well with the experimental data. The B(E2) values were also calculated and it was found that the calculated positive-parity low-spin state energy spectra of the odd-A Eu isotopes agree quite well with the experimental data.     

Q-Switching Pulse Generation with Thulium-Doped Fiber Saturable Absorber

Q-switched pulsed laser systems operating in the eye-safe wavelength region （λ〉 1.4 μm） are promis- ing for applications such as light detection and ranging （lidar）, differential absorption lidar, optical communi- cation, sensor and instrumentations. Fiber lasers are particularly attractive for such applications due to the fact that the beam quality can be independent of output power and they can be robustly engineered. There is an increasing interest in Q-switched erbium- doped fiber lasers （EDFLs）, which can be generated by using either active or passive techniques. Com- pared with the actively Q-switched ones, passively Q- switched EDFLs have attracted much attention for their advantages of compactness, low cost, flexibility and simplicity of design. Different kinds of saturable absorbers, such as the transition metal-doped crys- tals and semiconductor quantum-well structures, have been applied to realize Q-switched EDFLs.How- ever, when they are used in the laser cavity, additional alignment devices, such as lens, mirrors or U-bench units, have to be applied. This may increase the in- sertion loss and the complexity of the laser cavity.     

Photonic crystal ber-based multi-wavelength Brillouin ber laser with dual-pass ampli cation con guration

A simple technique for achieving a stable, room temperature and multi-wavelength lasing with narrow linewidth is demonstrated using Brillouin ber laser (BFL) with a 100-m-long photonic crystal ber (PCF) in conjunction with a dual-pass configuration. A broadband ber Bragg grating (FBG) operating in the C-band region is incorporated at the end side of the setup to allow a dual-pass operation. The proposed BFL can operate at any wavelength depending on the Brillouin pump wavelength and the FBG’s reflection region used. With a Brillouin pump (BP) of 15.7 dBm, approximately 7 Stokes and 4 anti-Stokes lines are obtained with a line spacing of 0.08 nm.     

Switchable Q-switched and mode-locked erbium-doped fiber laser operating in the L-band region

We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 μs, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least 10 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.     

Monitoring the Structure Evolution of Titanium Oxide Photocatalysts: From the Molecular Form via the Amorphous State to the Crystalline Phase

Amorphous Ti_xO_y with high surface area has attracted significant interest as photocatalyst with higher activity in ultraviolet (UV) light-induced water splitting applications compared to commercial nanocrystalline TiO₂. Under photocatalytic operation conditions, the structure of the molecular titanium alkoxide precursor rearranges upon hydrolysis and leads to higher connectivity of the structure-building units. Structurally ordered domains with sizes smaller than 7 Å form larger aggregates. The experimental scattering data can be explained best with a structure model consisting of an anatase-like core and a distorted shell. Upon exposure to UV light, the white Ti_xO_y suspension turns dark corresponding to the reduction of Ti⁴⁺ to Ti³⁺ as confirmed by electron energy loss spectroscopy (EELS). Heat-induced crystallisation was followed by in situ temperature-dependent total scattering experiments. First, ordering in the Ti−O environment takes place upon to 350 °C. Above this temperature, the distorted anatase core starts to grow but the structure obtained at 400 °C is still not fully ordered.     

Protein adsorption and transport in dextran-modified ion-exchange media. I: Adsorption

Adsorption behavior is compared on a traditional agarose-based ion-exchange resin and on two dextran-modified resins, using three proteins to examine the effect of protein size. The latter resins typically exhibit higher static capacities at low ionic strengths and electron microscopy provides direct visual evidence supporting the view that the higher static capacities are due to the larger available binding volume afforded by the dextran. However, isocratic retention experiments reveal that the larger proteins can be almost completely excluded from the dextran layer at high ionic strengths, potentially leading to significant losses in static capacity at relevant column loading conditions. Knowledge of resin and protein properties is used to estimate physical limits on the static capacities of the resins in order to provide a meaningful interpretation of the observed static capacities. Results of such estimates are consistent with the expectation that available surface area is limiting for traditional resins. In dextran-modified media, however, the volume of the dextran layer appears to limit adsorption when the protein charge is low relative to the resin charge, but the protein–resin electroneutrality may be limiting when the protein charge is relatively high. Such analyses may prove useful for semiquantitative prediction of maximum static capacities and selection of operating conditions when combined with protein transport information.     

Promoter Activation in Δhfq Mutants as an Efficient Tool for Specialized Metabolite Production Enabling Direct Bioactivity Testing

Natural products (NPs) from microorganisms have been important sources for discovering new therapeutic and chemical entities. While their corresponding biosynthetic gene clusters (BGCs) can be easily identified by gene‐sequence‐similarity‐based bioinformatics strategies, the actual access to these NPs for structure elucidation and bioactivity testing remains difficult. Deletion of the gene encoding the RNA chaperone, Hfq, results in strains losing the production of most NPs. By exchanging the native promoter of a desired BGC against an inducible promoter in Δhfq mutants, almost exclusive production of the corresponding NP from the targeted BGC in Photorhabdus, Xenorhabdus and Pseudomonas was observed including the production of several new NPs derived from previously uncharacterized non‐ribosomal peptide synthetases (NRPS). This easyPACId approach (easy Promoter Activated Compound Identification) facilitates NP identification due to low interference from other NPs. Moreover, it allows direct bioactivity testing of supernatants containing secreted NPs, without laborious purification.     

MIL‐53(Al) as a Versatile Platform for Ionic‐Liquid/MOF Composites to Enhance CO2 Selectivity over CH4 and N2

Five different imidazolium‐based ionic liquids (ILs) were incorporated into a metal–organic framework (MOF), MIL‐53(Al), to investigate the effect of IL incorporation on the CO₂ separation performance of MIL‐53(Al). CO₂, CH₄, and N₂ adsorption isotherms of the IL/MIL‐53(Al) composites and pristine MIL‐53(Al) were measured to evaluate the effect of the ILs on the CO₂/CH₄ and CO₂/N₂ selectivities of the MOF. Of the composite materials that were tested, [BMIM][PF₆]/MIL‐53(Al) exhibited the largest increase in CO₂/CH₄ selectivity, 2.8‐times higher than that of pristine MIL‐53(Al), whilst [BMIM][MeSO₄]/MIL‐53(Al) exhibited the largest increase in CO₂/N₂ selectivity, 3.3‐times higher than that of pristine MIL‐53(Al). A comparison of the CO₂ separation potentials of the IL/MOF composites showed that the [BMIM][BF₄]‐ and [BMIM][PF₆]‐incorporated MIL‐53(Al) composites both showed enhanced CO₂/N₂ and CO₂/CH₄ selectivities at pressures of 1–5 bar compared to composites of CuBTC and ZIF‐8 with the same ILs. These results demonstrate that MIL‐53(Al) is a versatile platform for IL/MOF composites and could help to guide the rational design of new composites for target gas‐separation applications.     

A Solid Phase Extraction Application of Hybrid Nano B_2O_3/ZrO_2 for Separation and Determination of Trace Indium in Environmental Samples

Hybrid nanomaterials have attracted considerable interest in environmental science, analytical chemistry and atomic spectroscopy. In the present study, a column solid phase extractioo procedure was developed for the separation and preconcentration of indium in various matrixes by using hybrid nanomaterial B₂O₃/ZrO₂ (HNMBZ). Various experimental and analytical parameters such as sample solution pH, sample solution volume, flow rate of sample solution and eluent, volume and concentration of eluent aod amount of HNMBZ, effect of common matrix ions and capacity of sorbent were investigated. The adsorbed metal ions on HNMBZ were eluted with 6 mL of 1 mol·L-1 HNO₃ solutions and their concentrations were determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Under the optimized conditions, detection limits for indium for 3 pixels and 5 pixels were found as 0.20 and 0.16 μg·L-1, respectively. The accuracy of the procedure was checked by spiked water samples. The developed procedure was successfully applied to real samples for the separation and determination of indium.