Engineering lattice matching, doping level, and optical properties of KY(WO4)2:Gd, Lu, Yb layers for a cladding-side-pumped channel waveguide laser

Single-crystalline KY_1?x?y?z Gd_xLu_yYb_z(WO₄)₂ layers are grown onto undoped KY(WO₄)₂ substrates by liquid-phase epitaxy. The purpose of co-doping the KY(WO₄)₂ layer with suitable fractions of Gd³⁺ and Lu³⁺ is to achieve lattice-matched layers that allow us to engineer a high refractive-index contrast between waveguiding layer and substrate for obtaining tight optical mode confinement and simultaneously accommodate a large range of Yb³⁺ doping concentrations by replacing Lu³⁺ ions of similar ionic radius for a variety of optical amplifier or laser applications. Crack-free layers, up to a maximum lattice mismatch of ~0.08 %, are grown with systematic variations of Y³⁺, Gd³⁺, Lu³⁺, and Yb³⁺ concentrations, their refractive indices are measured at several wavelengths, and Sellmeier dispersion curves are derived. The influence of co-doping on the spectroscopy of Yb³⁺ is investigated. As evidenced by the experimental results, the lattice constants, refractive indices, and transition cross-sections of Yb³⁺ in these co-doped layers can be approximated with good accuracy by weighted averages of data from the pure compounds. The obtained information is exploited to fabricate a twofold refractive-index-engineered sample consisting of a highly Yb³⁺-doped tapered channel waveguide embedded in a passive planar waveguide, and a cladding-side-pumped channel waveguide laser is demonstrated.     

Chalcogeno[bis(phosphaalkenyl)] germanium and tin compounds

The first diphosphaalkenylstannylene stabilized through complexation with a carbene NHC-Sn[C(Cl)═PMes*](2)1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC = :C{N(iPr)C(Me)}(2)) was isolated and fully characterized including single crystal X-ray diffraction analysis. Its reaction with elemental sulfur rapidly gives the cyclic Sn(2)S(2) (dithiadistannetanne) derivative 3, presumably formed by dimerization of a stannathione intermediate. By contrast, its germanium analogue NHC-Ge[C(Cl)═PMes*](2)7 leads to the corresponding monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the Ge(2)Se(3) (triselenadigermolane) ring derivative 6.     

Phosphaalkenyl germylenes and their gold, tungsten and molybdenum complexes

The new bis(phosphaalkenyl) germanium(II) compound (NHC)Ge(CCl=PMes*)(2) reacts with L(2)M(CO)(4) (M = Mo, W) to give bidentate complexes with an unexpected coordinating behaviour involving the Ge(II) centre and one phosphorus atom, and with AuI or Me(2)SAuCl to afford the monodentate complexes coordinated at the germanium(II) atom.     

Metallacrowns of Ni(II) with α-aminohydroxamic acids in aqueous solution: beyond a 12-MC-4, an unexpected (vacant?) 15-MC-5

Growing attention has been devoted in the recent years to a class of metallamacrocycles known as metallacrowns (MCs). They are structural analogues of crown ethers where the methylene bridges have been substituted by coordinative bonds formed by a transition metal ion ("ring" metal) and a nitrogen atom. The cavity of the metallacrown can accommodate an additional metal ion ("core" metal) either identical or different from the ring metal, thus forming a homo- or hetero-metallic MC. The most studied ring metal ion is certainly Cu(2+) and the aminohydroxamic acids have proved to be very suitable ligands to form MCs. The behavioural analogies between Cu(2+) and Ni(2+) in forming complexes, along with recent literature data in the solid state, prompted us to investigate the possible MC formation between Ni(2+) and both (S)-α-alaninehydroxamic acid and (S)-valinehydroxamic acid, in aqueous solution. Two metallacrowns, a 12-MC-4 and an unexpected 15-MC-5 have been detected by potentiometry and confirmed by ESI-MS results. Their structures are discussed on the basis of potentiometric, calorimetric, spectroscopic data and DFT calculations. The existence of a vacant 15-MC-5 species in solution can be put forward for the first time, making the present metal/ligand systems very interesting for their potential applications in cation recognition and separation. Finally, the crystal structure of the binary complex K[NiL(2)H(-1)]·5/3 H(2)O of (S)-α-alaninehydroxamic acid (LH) is also reported.     

Maximum principles for anisotropic elliptic inequalities

We establish some maximum and comparison principles for weak distributional solutions of anisotropic elliptic inequalities in divergence form, both in the homogeneous and non-homogeneous cases. The main prototypes we have in mind are inequalities involving the p(⋅)$p(\cdot )$-Laplace operator and the generalized mean curvature operator.     

Self‐Assembly of a Low‐Symmetry Monodendron Containing Two Asymmetrically Linked Molecular Wedges

Herein, we describe the synthesis of a low‐symmetry monodendron, 3,4‐bis(dodecyloxy)‐5‐[3,4,5‐tris(dodecyloxy)benzyloxy]benzoic acid, following a simple route which starts from gallic acid ethyl ester and does not require any protecting groups. The self‐assembled structures formed by the compound in 3D and 2D were investigated by synchrotron X‐ray scattering and scanning force microscopy (SFM). In 3D, the compound forms a stable crystalline phase with an orthorhombic lattice in which the alkyl chains connected to different benzene rings form crystalline and amorphous domains. Upon cooling from the isotropic melt the compound exhibits a monotropic smectic mesophase. In 100‐nm‐thick films on a neutral substrate the structure loses its biaxiality, adopting a hexagonal columnar structure with the columns oriented parallel to the substrate. By contrast, in ultrathin films on graphite the SFM likely reveals two crystal orientations, which can develop due to the epitaxial adsorption on the substrate of the alkyl chains pertinent to different benzene rings.     

The effects of flow type on aptamer capture in differential mobility cytometry cell separations

In this work, differential mobility cytometry (DMC) was used to monitor cell separation based on aptamer recognition for target cells. In this device, open-tubular capillaries coated with Sgc8 aptamers were used as affinity chromatography columns for separation. After cells were injected into the columns, oscillating flow was generated to allow for long-term cell adhesion studies. This process was monitored by optical microscopy, and differential imaging was used to analyze the cells as they adhered to the affinity surface. We investigated the capture time, capture efficiency, purity of target and control cells, as well as the reusability of the affinity columns. Capture time for both CCRF-CEM cells and Jurkat T cells was 0.4 ± 0.2 s, which demonstrated the high separation affinity between aptamers and target cells. The capture efficiency for CCRF-CEM cells was 95% and purity was 99% in a cell mixture. With the advantage of both high cell capture efficiency and purity, DMC combined with aptamer-based separation emerges as a powerful tool for rare cell enrichment. In addition, aptamer-based DMC channels were found to be more robust than antibody based channels with respect to reuse of the separation device.     

Early detection of apoptosis in living cells by fluorescence correlation spectroscopy

Early detection of apoptotic cells via caspase activity is demonstrated with fast response time. Fluorescence correlation spectroscopy (FCS) is used to identify the presence of a cleaved fluorogenic probe based on the fluorescence of rhodamine 110 in Jurkat cells. FCS curves are shown to be markedly different for autofluorescent (non-apoptotic) cells, whereas cells with cleaved probe showed diffusion and molecular brightness characteristic of rhodamine 110. Using FCS measurements, cells were identified as apoptotic on the basis of the presence of autocorrelated fluorescence, average molecular brightness (η), and molecular dwell time (τ _D). Apoptotic cells identified in this manner were detected as early as 45 min after induction. Unlike other methods with similar identification times, such as western blotting and electron microscopy, cells remain viable for further analysis. This multi-parameter approach is rapid, flexible, and does not require transfection of the cells prior to analysis, enabling apoptosis to be identified early in a wide variety of cell types.