Evidence for Fisher renormalization in the compressible phi4 model

We present novel Fourier Monte Carlo simulations of a compressible phi4-model on a simple-cubic lattice with linear-quadratic coupling of order parameter and strain, focusing on the detection of fluctuation-induced first-order transitions and deviations from standard critical behavior. The former is indeed observed in the constant stress ensemble and for auxetic systems at constant strain, while for regular isotropic systems at constant strain, we find strong evidence for Fisher-renormalized critical behavior and are led to predict the existence of a tricritical point.     

High-power laser diodes emitting light above 1100 nm with a small vertical divergence angle of 13 degrees

Laser diodes with highly strained InGaAs quantum wells, emitting at 1130 nm, embedded in a GaAs waveguide were investigated. This Letter reviews the design of the vertical structure for enclosing high output power in angles smaller than 18 degrees . Example designs were processed to 200 microm stripe-width lasers with an 8-mm-long optical cavity. When these are mounted on C mounts, they give an output power of 38 W under quasi-cw operation from a single emitter.     

Cytotoxic dimeric half-sandwich Ru(II), Os(II) and Ir(III) complexes containing the 4,4′-biphenyl-based bridging ligands

A series of dinuclear half-sandwich Ru(II), Os(II) and Ir(III) complexes [Ru₂(μ-Lⁿ)(η⁶-pcym)₂Cl₂](PF₆)₂ ( 1 , 4 ), [Os₂(μ-Lⁿ)(η⁶-pcym)₂Cl₂](PF₆)₂ ( 2 , 5 ) and [Ir₂(μ-Lⁿ)(η⁵-Cp*)₂Cl₂](PF₆)₂ ( 3 , 6 ), based on 4,4′-biphenyl-based bridging Schiff base ligands N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)methanamine (L¹; for 1 – 3 ) and N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)ethanamine (L²; for 4 – 6 ) is reported; pcym = 1-methyl-4-(propan-2-yl)benzene, Cp* = pentamethylcyclopentadienyl. The complexes were characterized by relevant analytical techniques (i.e. elemental analysis, FT-IR, NMR, ESI-MS), and their in vitro cytotoxicity was assessed at six cancerous and two non-cancerous (healthy) human cell lines. Overall, complexes 4 – 6 , containing the L² bridging ligand, revealed higher cytotoxicity as compared with 1 – 3 and, thus, they were studied in greater detail. The best-performing complex 6 exceeded at least twice the in vitro cytotoxicity of cisplatin and showed high selectivity towards the cancer cells over the normal ones, including the primary culture of human hepatocytes. In contrast to cisplatin, complexes 4 – 6 did not induce the cell cycle modification of the treated A2780 human ovarian carcinoma cells (studied by flow cytometry and Western blot analysis). High levels of superoxide anion were induced by complexes 4 – 6 at the A2780 cells. The levels of activated forms of Caspase-3 and Caspase-8 at the A2780 cells treated by Ru(II) complex 4 were comparable with cisplatin, while complexes 5 and 6 had only a minor effect on activation of these caspases.     

Capillary electrophoresis with inductively coupled plasma-mass spectrometric and electrospray time of flight mass spectrometric detection for the determination of arsenic species in fish samples

CE was coupled to inductively coupled plasma MS (ICP-MS) and ESI-MS to identify and quantify the arsenic species arsenobetaine (AsB), arsenite (As(III)), arsenate (As(V)), and dimethylarsinic acid (DMA). A GC-flame ionization detector (FID)-based German standard method and ICP-MS were used for validation of the data obtained for arsenobetaine and total arsenic, respectively. LODs obtained with the CE-ESI-TOF-MS method were 1.0x10(-7) M for AsB, 5.0x10(-7) M for DMA, and 1.0x10(-6) M for As(III) and As(V). For the CE-ICP-MS method, LODs were 8.5x10(-8) M for AsB, 9.5x10(-8) M for DMA, 9.3x10(-8) M for As(III), and 6.2x10(-8) M for As(V). While CE-ICP-MS provided high sensitivity and better reproducibility for quantitative measurements, CE-ESI-MS with a TOF mass analyzer proved to be valuable for species identification. With this setup, fish samples were prepared and analyzed and the obtained data were successfully validated with the independent methods.     

Multi-residue determination of seven quinolones antibiotics in gilthead seabream using liquid chromatography-tandem mass spectrometry

A sensitive and selective confirmatory analytical method for the multi-residue determination of seven quinolones (ciprofloxacin, enrofloxacin, sarafloxacin, danofloxacin, oxolinic acid, nalidixic acid and flumequine) in gilthead seabream (Sparus aurata) was developed. The sample pre-treatment involves extraction with 0.1M NaOH and purification by solid-phase extraction (SPE) on Waters Oasis HLB cartridges followed by the determination of all compounds in a single LC-electrospray ionization MS/MS run. Separation was achieved on a Perfectsil ODS-2, 5mum, 250mmx4mm, analytical column (MZ Analysentechnik) by gradient elution using a mixture of 0.2% (v/v) formic acid, methanol and acetonitrile within 30min. Multiple reaction monitoring (MRM) was used for selective detection of each quinolone. Accuracy was evaluated through recovery studies at three different fortification levels. The mean recoveries are between 90 and 132% for the selected levels with RSD values lower than 20%. The method presents satisfactory results for linearity, precision and limits of quantification. The latter are much lower than the maximum residue limits (MRLs) established by the European Union for quinolones in fish tissues (6-8mug/kg).     

Synthesis of hybrid gold-gold sulfide colloidal particles

The nucleation and growth mechanism of nanometer size gold onto gold sulfide colloidal particles by irradiation-induced reduction is reported. The process is characterized by ultraviolet-visible spectroscopy, electronic diffraction, and high-resolution transmission electron microscopy, allowing for observation of several key intermediates and characteristics of the growth mechanism. The formation mechanism of gold on the surface of the gold sulfide particles is shown to depend strongly on the deposition rate. At low dose rate, gold nucleates preferentially onto specific gold-rich Au2S facets {110}, resulting in epitaxial growth. The gold crystal lattice plastically deforms near the interface to accommodate a substantial lattice mismatch. Upon increasing gold precursor concentration, this low dose rate results in growth of elongated gold island on the gold sulfide surface. At a high dose rate, several randomly oriented gold particles are simultaneously produced on gold sulfide, resulting in a layered structure. The absorption spectra of these particles show a dominant surface plasmon band, whose peak wavelength shifts markedly to the red as layered structure is formed.