Observation of vinylidene emission in mixed phosphine/diimine complexes of Ru(II) at room temperature in solution

The mixed ruthenium(II) complexes trans-[RuCl(2)(PPh(3))(2)(bipy)] (1), trans-[RuCl(2)(PPh(3))(2)(Me(2)bipy)](2), cis-[RuCl(2)(dcype)(bipy)](3), cis-[RuCl(2)(dcype)(Me(2)bipy)](4) (PPh(3) = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2'-bipyridine, Me(2)bipy = 4,4'-dimethyl-2,2'-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(=C=CHPh)(PPh(3))(2)(bipy)]PF(6) (5), [RuCl(=C=CHPh)(PPh(3))(2)(Me(2)bipy)]PF(6) (6), [RuCl(=C=CHPh)(dcype)(bipy)]PF(6) (7), [RuCl(=C=CHPh)(dcype)(bipy)]PF(6) (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the pi-pi* excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH(2)Cl(2), CH(3)CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(-0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry. (C) 2011 Elsevier B.V. All rights reserved.

Ultrasound-assisted synthesis of aliphatic acid esters at room temperature

This work describes the ultrasound-assisted synthesis of saturated aliphatic esters from synthetic aliphatic acids and either methanol or ethanol. The products were isolated in good yields after short reaction times under mild conditions. (C) 2011 Elsevier BM. All rights reserved.

An electrochemical gas sensor based on paper supported room temperature ionic liquids

A sensitive and fast-responding membrane-free amperometric gas sensor is described, consisting of a small filter paper foil soaked with a room temperature ionic liquid (RTIL), upon which three electrodes are screen printed with carbon ink, using a suitable mask. It takes advantage of the high electrical conductivity and negligible vapour pressure of RTILs as well as their easy immobilization into a porous and inexpensive supporting material such as paper. Moreover, thanks to a careful control of the preparation procedure, a very close contact between the RTIL and electrode material can be achieved so as to allow gaseous analytes to undergo charge transfer just as soon as they reach the three-phase sites where the electrode material, paper supported RTIL and gas phase meet. Thus, the adverse effect on recorded currents of slow steps such as analyte diffusion and dissolution in a solvent is avoided. To evaluate the performance of this device, it was used as a wall-jet amperometric detector for flow injection analysis of 1-butanethiol vapours, adopted as the model gaseous analyte, present in headspace samples in equilibrium with aqueous solutions at controlled concentrations. With this purpose, the RTIL soaked paper electrochemical detector (RTIL-PED) was assembled by using 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide as the wicking RTIL and printing the working electrode with carbon ink doped with cobalt(II) phthalocyanine, to profit from its ability to electrocatalyze thiol oxidation. The results obtained were quite satisfactory (detection limit: 0.5 mu M; dynamic range: 2-200 mu M, both referring to solution concentrations; correlation coefficient: 0.998; repeatability: +/- 7% RSD; long-term stability: 9%), thus suggesting the possible use of this device for manifold applications.

Study of the oxygen vacancy influence on magnetic properties of Fe- and Co-doped SnO2 diluted alloys

Transition-metal (TM)-doped diluted magnetic oxides (DMOs) have attracted attention from both experimental and theoretical points of view due to their potential use in spintronics towards new nanostructured devices and new technologies. In the present work, we study the magnetic properties of Sn0.96TM0.04O2 and Sn0.96TM0.04O1.98(V (O))(0.02), where TM = Fe and Co, focusing in particular in the role played by the presence of O vacancies nearby the TM. The calculated total energy as a function of the total magnetic moment per cell shows a magnetic metastability, corresponding to a ground state, respectively, with 2 and 1 mu(B)/cell, for Fe and Co. Two metastable states, with 0 and 4 mu(B)/cell were found for Fe, and a single value, 3 mu(B)/cell, for Co. The spin-crossover energies (E (S)) were calculated. The values are E (S) (0/2) = 107 meV and E (S) (4/2) = 25 meV for Fe. For Co, E (S) (3/1) = 36 meV. By creating O vacancies close to the TM site, we show that the metastablity and E (S) change. For iron, a new state appears, and the state with zero magnetic moment disappears. The ground state is 4 mu(B)/cell instead of 2 mu(B)/cell, and the energy E (S) (2/4) is 30 meV. For cobalt, the ground state is then found with 3 mu(B)/cell and the metastable state with 1 mu(B)/cell. The spin-crossover energy E (S) (1/3) is 21 meV. Our results suggest that these materials may be used in devices for spintronic applications that require different magnetization states.

Tuning Low-Spin to High-Spin Mn Pairs in 2-D ZnO by Injecting Holes

We have performed an ab initio theoretical investigation of substitutional Mn(Zn) atoms in planar structures of ZnO, viz., monolayer [(ZnO)(1)] and bilayer [(ZnO)(2)] systems. Due to the 2-D quantum confinement effects, in those Mn -doped (ZnO)(1) and (ZnO)(2) structures, the antiferromagnetic (AFM) coupling between (nearest neighbor) Mn(Zn) impurities have been strengthened when compared with the one in ZnO bulk systems. On the other hand, we find that the magnetic state of these systems can be tuned from AFM to FM by adding holes, which can be supplied by a p-type doping or even photoionization processes. Whereas, upon addition of electrons (n-type doping), the system keeps its AFM configuration.

Influence of light, temperature and metallic ions on biodiesel degradation and corrosiveness to copper and brass

Corrosion is a relevant issue regarding the problem of biodiesel compatibility with polymers and metals. This work aims to evaluate the influence of the natural light incidence and temperature in the corrosion rate of brass and copper immersed in commercial biodiesel as well as biodiesel degradation after the contact with metallic ions. The characterization of corrosion behavior was performed by weight loss measurements according to ASTM G1 and ASTM G31. The experiments according to ASTM G1 were performed at room temperature in light presence and absence. Experiments were also conducted at 55 degrees C in order to compare with ASTM G31 that is also performed at that temperature. The biodiesel degradation was characterized by water content, oxidation stability, viscosity as well as XRF, IR and Raman spectroscopies. The results of ASTM G1 tests showed that the thickness loss for both metals determined at room temperature is slightly higher when there is light incidence and these values significantly decrease for the highest temperature. The results of ASTM G31 tests indicated that air bubbling along with higher temperature affects mostly immersed samples. Biodiesel in contact with metals shows significant degradation in its properties as evidenced by increasing water content, higher viscosity and lower oxidation stability. (C) 2012 Elsevier Ltd. All rights reserved.

Oocyte meiotic-stage-specific differences in spindle depolymerization in response to temperature changes monitored with polarized field microscopy and immunocytochemistry

Objective: To compare the polymerization status of mouse oocyte spindles exposed to various temperatures at various stages of meiosis. Design: Experimental animal study. Setting: University animal laboratory. Animal(s): CF1 mice. Intervention(s): Immature oocytes matured to metaphase I (MI), telophase I (TI), and metaphase II (MII) were incubated at 37 degrees C (control), room temperature (RT), or 4 degrees C for 0, 10, 30, and 60 minutes. Spindle analysis subsequently was performed using polarized field microscopy and immunocytochemistry. Spindles of TI and MII oocytes that underwent vitrification and warming were analyzed also by immunocytochemistry. Main Outcome Measure(s): Detection of polymerized meiotic spindles. Result(s): At RT, and after 60 minutes at 4 degrees C, a significant time-dependent decrease in the percentage of polymerized meiotic spindles was observed in MI and MII oocytes, but not in TI oocytes. The polymerization of TI spindles at 4 degrees C was similar to that of TI spindles at 4 degrees C that underwent vitrification and warming. Conclusion(s): Significant differences in the microtubule dynamics of MI, TI, and MII oocytes incubated at different temperatures were observed. In particular, meiotic spindles in TI oocytes exhibited less depolymerization than did metaphase spindles. (Fertil Steril (R) 2012; 97: 714-9. (C) 2012 by American Society for Reproductive Medicine.)

The effect of sodium fluoride preservative and storage temperature on the stability of cocaine in horse blood, sheep vitreous and deer muscle

The in vitro stability of cocaine in horse blood, sheep vitreous humour (VH) and homogenised deer muscle is described. The stability of cocaine in horse blood was of interest because many toxicology laboratories utilise horse blood for the preparation of calibration and check standards and the latter are typically stored during routine use. The storage stability of cocaine in human VH and muscle has not been previously reported. In the absence of blank human VH and muscle, cocaine stability under varying conditions was demonstrated in animal tissues. Blood and VH were stored with and without addition of NaF at room temperature (RT), 4 degrees C and -18 degrees C for 84 days. Muscle homogenates were prepared in water, water/2% NaF, and phosphate buffer (pH 6.0)/2% NaF, and stored for 31 days at RT, 4 degrees C and -18 degrees C. Cocaine stability in human muscle obtained from cocaine positive forensic cases was assessed following storage at -18 degrees C for 13 months. Cocaine and benzoylecgonine (BZE) were extracted using SPE and quantified by GC-MS/MS. Cocaine was stable for 7 days in refrigerated (4 degrees C) horse blood fortified with 1 and 2% NaF. In the absence of NaF, cocaine was not detectable by day 7 in blood stored at RT and 4 degrees C and had declined by 81% following storage at -18 degrees C. At 4 degrees C the rate of cocaine degradation in blood preserved with 2% NaF was significantly slower than with 1% NaF. The stability of cocaine in horse blood appeared to be less than that reported for human blood, probably attributable to the presence of carboxylesterase in horse plasma. Cocaine stored in VH at -18 degrees C was essentially stable for the study period whereas at 4 degrees C concentrations decreased by >50% in preserved and unpreserved VH stored for longer than 14 days. Fluoride did not significantly affect cocaine stability in VH. The stability of cocaine in muscle tissue homogenates significantly exceeded that in blood and VH at every temperature. In preserved and unpreserved samples stored at 4 degrees C and below, cocaine loss did not exceed 2%. The increased stability of cocaine in muscle was attributed to the low initial pH of post-mortem muscle. In tissue from one human case stored for 13 months at -18 degrees C the muscle cocaine concentration declined by only 15% (range: 5-22%). These findings promote the use of human muscle as a toxicological specimen in which cocaine may be detected for longer compared with blood or VH. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Effect of temperature and storage time on cellular analysis of fresh pleural fluid samples

L. Antonangelo, F. S. Vargas, M. M. P. Acencio, A. P. Cora, L. R. Teixeira, E. H. Genofre and R. K. B. Sales Effect of temperature and storage time on cellular analysis of fresh pleural fluid samples Objective: Despite the methodological variability in preparation techniques for pleural fluid cytology, it is fundamental that the cells should be preserved, permitting adequate morphological classification. We evaluated numerical and morphological changes in pleural fluid specimens processed after storage at room temperature or under refrigeration. Methods: Aliquots of pleural fluid from 30 patients, collected in ethylenediaminetetraacetic acid-coated tubes and maintained at room temperature (21 degrees C) or refrigeration (4 degrees C) were evaluated after 2 and 6 hours and 1, 2, 3, 4, 7 and 14 days. Evaluation of cytomorphology and global and percentage counts of leucocytes, macrophages and mesothelial cells were included. Results: The samples had quantitative cellular variations from day 3 or 4 onwards, depending on the storage conditions. Morphological alterations occurred earlier in samples maintained at room temperature (day 2) than in those under refrigeration (day 4). Conclusions: This study confirms that storage time and temperature are potential pre-analytical causes of error in pleural fluid cytology.