Abstract  In this paper, we focus on improvement of the monovalent cation perm-selectivity of a perfluorinated cation-exchange membrane, Nafion 117, by depositing an anion-exchange layer using a plasma surface modification process. The anion-exchange layer was deposited from 4-vinylpyridine monomer vapor followed by quaternization with 1-bromopropane. The transference number of divalent cation (Fe2+) through the membrane, t(Fe), decreased with increasing thickness of the plasma polymer layer at the expense of enhanced membrane resistance. A large interfacial resistance was observed between Nafion and the plasma polymer layer which was ascribed to the implantation of cationic species containing nitrogen. To avoid the formation of an interfacial layer, a novel method of plasma-induced surface modification was devised. After a Nafion 117 sheet was placed on an RF (radio-frequency) electrode and sputtered with an oxygen or argon plasma in order to produce active sites on the Nafion, 4-vinylpyridine or 3-(2-aminoethyl)aminopropyltrimethoxysilane vapor was introduced into the reactor to react with radical sites. t(Fe) decreased with increasing RF power. t(Fe) through Nafion modified with 3-(2-aminoethyl)aminopropyltrimethoxysilane was lower than that for Nafion modified with 4-vinylpyridine, probably due to its weak Si-C bond. Nafion treated by the plasma surface modification method exhibited a very high monovalent cation perm-selectivity compared with Nafion treated by the plasma polymerization method.

Abstract  Centrifuge extraction and Rotavapor recovery were used to determine the effect of solvent type (trichloroethylene and four n-propyl bromide products) on recovered asphalt binder properties. Mix variables included three binders mixed with each of two aggregate sources (one gradation). When recovered binder properties were compared to the original binder properties, the trichloroethylene solvent combined with the extraction and recovery processes occasionally produced higher (i.e., stiffer) recovered binders. One n-propyl bromide product appeared to be incompatible with the polymer-modified PG 76-22. This incompatibility was seen as a distinct stringy, rubber-like residue in the extractor. Fourier transform infrared analysis showed that this same product also seemed to inhibit or actually limit normal heat-related changes. Overall, the data indicate that n-propyl bromide solvents can be used as direct replacements for the chlorinated solvents historically used for hot-mix asphalt extraction and binder recovery.

Abstract  This paper presents methods for the surface modification of cotton woven fabric and polypropylene non-woven in order to make them antibacterial. In the case of cotton fabric, its surface was functionalised with chloroacetate groups by means of chloroacetyl chloride, using pyridine as a catalyst, followed by the quaternalisation of the chloroacetate groups with poly(4-vinylpyridine). In the second process polypropylene nonwoven was impregnated with a multimonomer containing vinyl groups, which were then changed into tertiary amine groups by the addition of diethylamine. These groups were quaternalised with propyl bromide. In the next method colloidal silver was incorporated into the nanolayers formed from polyelectrolytes on the polypropylene non-woven. Quantitative tests of bacteriological activity of the modified woven fabric and non-woven showed both bacteriostatic and bactericidal activities in relation to Escherichia coli. In addition, colloidal platinum was incorporated into previously deposited polyelectrolyte nanolayers in order to impart catalytic properties to fibers. The results obtained clearly show the catalytic action of such systems, the oxygen release from the hydrogen peroxide solution being an example.

Abstract  The heat capacity and parameters of fusion of 1-bromobutane (BuBr) were measured in the temperature range (5 to 370) K using adiabatic calorimetry. The thermodynamic functions for the compound in the crystal and liquid states were calculated from these data. On the basis of the experimental spectroscopic data and the results of quantum-chemical calculations, the ideal-gas properties for BuBr were calculated by methods of statistical thermodynamics. The obtained entropy S(m)degrees(g; 298.15 K) = 366.9 J.K(-1).mol(-1) is in excellent agreement with the value 367.0 +/- 1.2 J.K(-1).mol(-1) obtained from the experimental data. The ideal-gas thermodynamic properties were also calculated for isomeric bromobutanes and 1-butyl-3-methylimdiazolium bromide ionic liquids that allowed us to find the changes of thermodynamic properties in the reactions of synthesis of 1-butyl-3-methylimidazolium bromide isomers. The literature data on the enthalpies of formation for isomeric bromobutanes were collected, and the recommended values were developed. It was demonstrated that the synthesis of ionic liquids from bromoalkanes and 1-methylimidazole in the gas phase, unlike the liquid-phase reaction, is not a thermodynamically favorable process. It possesses more positive enthalpy changes and more negative entropy changes compared to the synthesis in the liquid phase.

Abstract  The rate constant for the gas phase reaction of OH radicals with BTP (2-bromo-3,3,3-trifluoropropene, CH2 = CBrCF3) was measured using a flash photolysis resonance-fluorescence technique over the temperature range 220 K to 370 K. The Arrhenius plot was found to exhibit noticeable curvature. The temperature dependence of the rate constant can be represented as k(BTP)(220 - 370 K) = 4.85 x 10(-13) x (T/298)(0.92) x exp{+613/T} cm(3) molecule(-1) s(-1). For atmospheric modeling purposes, k(BTP)(T) can be equally well represented by the standard Arrhenius expression k(BTP)(220 - 298 K) = 1.05 x 10(-12) x exp{+381/T} cm(3) molecule(-1) s(-1). The IR absorption cross-sections of BTP were also measured between 450 cm(-1) and 1900 cm(-1). BTP atmospheric lifetime, Ozone Depletion Potential (ODP), and Global Warming Potential (GWP) were evaluated in the Whole Atmosphere Community Climate Model for land emissions from 30 to 60 degrees N and from 60 degrees S to 60 degrees N. The global, annual average atmospheric lifetime of BTP in the former scenario was 7.0 days, its ODP was 0.0028, and its GWP (100-yr time horizon) was 0.0050; in the latter scenario, the global, annual average BTP lifetime was 4.3 days, ODP was 0.0052, and 100-yr GWP was 0.0028. The short lifetime, low ODP, and low GWP indicate that BTP should have minimal effects on ozone and climate. Little BTP reaches the stratosphere in either emission scenario, but 27% of the ozone loss in the 30 to 60 degrees N scenario and 46% of the ozone loss in the 60 degrees S to 60 N scenario occurs above the tropopause due to Br-y from BTP.

Abstract  The purposes of the present study are (1) to develop a sensitive analytical method to measure 1-bromopropane (1-BP) in urine, (2) to examine if 1-BP or bromide ion (Br) in urine is a useful biomarker of exposure to 1-BP, and (3) to identify the lowest 1-BP exposure concentration the method thus established can biomonitor. A factory survey was carried out on Friday, and 33 workers (all men) in cleaning and painting workshops participated; each worker was equipped with a diffusive sampler (carbon cloth KF-1500 as an adsorbent) to monitor 1-BP vapour for an 8-h shift, and offered a urine sample at the end of the shift for measurement of 1-BP and Br in urine. In addition, 10 non-exposed men offered urine samples as controls. The performance of the carbon cloth diffusive sampler was examined to confirm that the sampler is suitable for monitoring time-weighted average 1-BP vapour exposure. A head-space GC technique was employed for analysis of 1-BP in urine, whereas Br in urine was analysed by ECD-GC after derivatization to methyl bromide. The workers were exposed to vapours of seven other solvents (i.e. toluene, xylenes, ethylbenzene, acetone, etc.) in addition to 1-BP vapour; the 1-BP vapour concentration was 1.4 ppm as GM and 28 ppm as the maximum. Multiple regression analysis however showed that 1-BP was the only variable that influenced urinary 1-BP significantly. There was a close correlation between 1-BP in urine and 1-BP in air; the correlation coefficient (r) was >0.9 with a narrow variation range, and the regression line passed very close to the origin so that 2 ppm 1-BP exposure can be readily biomonitored. The correlation of Br in urine with 1-BP in air was also significant, but the r (about 0.7) was smaller than that for 1-BP, and the background Br level was also substantial (about 8 mg l-1). Thus, it was concluded that 1-BP in end-of-shift urine is a reliable biomarker of occupational exposure to 1-BP vapour, and that Br in urine is less reliable.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM NOTE RESEARCH ARTICLE WISTAR RAT MALE FEMALE 1-BROMOPROPANE TOXICOKINETICS TOXICITY HEPATIC METABOLISM PARTITION COEFFICIENT ANEMIA AMENORRHEA OLIGOSPERMIA HEPATIC MICROSOMES 2-BROMOPROPANE TOXICOLOGY BLOOD AND LYMPHATIC DISEASE REPRODUCTIVE SYSTEM DISEASE-FEMALE REPRODUCTIVE SYSTEM DISEASE-MALE KOREA PALEARCTIC REGION

Abstract  To investigate the effects on the central nervous system of subchronic exposure to 1-bromopropane (1-BP), which is a substitute for chlorofluorocarbons, we measured the hippocampal excitability of 1-BP-treated rats electrophysiologically. Male Wistar rats were exposed to 1-BP for 6-h in a day in an exposure chamber (1,500 ppm) for 4 wk. After the 1-, 3- and 4-wk inhalation, field excitatory postsynaptic potentials (fEPSPs), population spikes (PSs), fEPSP/spike (E/S) curve, paired-pulse profiles of fEPSP slopes and PS amplitudes recorded from CA1 pyramidal neurons, and dentate granule cells of the hippocampal slice obtained from the rats were analyzed. In 1-BP treated rats, E/S potentiation and a lower subthreshold of PSs were observed in the dentate gyrus (DG) after the 3 and 4-wk inhalation. Paired-pulse inhibition was reduced at 5-50 ms in the CA1 and at 5-20 ms in the DG after all of the inhalation. These changes were not associated with paired-pulse inhibition of fEPSPs. In the DG, the paired-pulse inhibition at the short interpulse intervals in rats exposed to 1-BP was pronounced by an application of A type gamma aminobutyric acid (GABA) receptor agonist pentobarbital. Impaired paired-pulse inhibition of granule cells at the short interpulse intervals was recovered after the application of N-methyl-D-aspartate (NMDA) type glutamate receptor antagonist DL-2-amino-5-phosphonopentanoic acid. Convulsing rats observed after the 4-wk inhalation exhibited multiple PSs in the DG, and their second component was abolished by an application of this antagonist. Inhalation of 1-BP increased the neuronal excitability in the hippocampal CA1 and the DG. The hyperexcitability of the granule cells in the DG was at least due to an over-activation of NMDA receptors.

Abstract  A Monte Carlo simulation using a diffusion based exposure assessment model was employed to aid forecasting of solvent vapour concentrations in the workspace during wipe cleaning of metal components. Range values for the important variables were chosen so as to be appropriated for wipe cleaning with either highly volatile solvents such as Vertrel-MCA or HFE71DE or with less volatile solvents such as n-propylbromide (nPBr). Emphasis is put on confirming that the range values of variables and the distributions taken are applicable to the workplace environment so that the simulation values obtained are reasonable estimates of the true vapour concentrations. The results obtained using Monte Carlo forecasts are considered most useful when taken in conjunction with the relevant occupational exposure limits for the solvents in question.

Abstract  In this study, a lipase from the liver of Cyprinus carpi Linnaeus (1758) living in Todurge Lake (Sivas) was purified with purification parameters of 90.38 mu mol/dk.mg protein specific activity and 75.50 fold purity. The purification procedure consisted of preparation of homogenate, precipitation with polyethylene glycol-6000 (PEG-6000) and chromatographic techniques including in Q sepharose, sephacryl S 200 HR and phenyl sepharose CL-4B, respectively. The purified lipase showed a single band with approximately a molecular weight of 74 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). pH and temperature optimums for the purified enzyme were determined as 8 and 37 degrees C using p-nitrophenyl butirate (p-NPB) as substrate. K-m and V-max values were found as 0.17 mM p-NPB and 2.6 mu mol/ml.dk, respectively. It was observed that surface active agents, such as sodium dodecyl sulfate (SDS), Triton X-100 and Nataurocholate act as inhibitor on lipase activity.

Abstract  Heterotrophic bacterial and phytoplankton biomass, production, specific growth rates, and growth efficiencies were studied in the Northern region of the Cananeia-Iguape estuarine system, which has recently experienced an intense eutrophication due to anthropogenic causes. Two surveys were carried out during spring and neap tide periods of the dry season of 2005 and the rainy season of 2006. This region receives large freshwater inputs with organic seston and phosphate concentrations that reach as high as 1.0 mg l(-1) and 20.0 mu M, respectively. Strong decreasing gradients of seston and dissolved inorganic nutrients were observed from the river/estuary boundary to the estuary/coastal interface. Gradients were also observed in phytoplankton and bacterial production rates. The production rates of phytoplankton were 5.6-fold higher (mean 8.5 mu g Cl(-1) h(-1)) during the dry season. Primary production rates (PP) positively correlated with salinity and euphoric depth, indicating that phytoplankton productivity was light-limited. On the other hand, bacterial biomass (BB) and production rates (BP) were 1.9- and 3.7-fold higher, respectively, during the rainy season, with mean values of up to 40.4 mu g Cl(-1) and 7.9 mu g Cl(-1) h-1, respectively. Despite such a high BP, bacterial abundance remained <2 x 106 cells ml(-1), indicating that bacterial production and removal were coupled. Mean specific growth rates ranged between 0.9 and 5.5 d(-1). BP was inversely correlated with salinity and positively correlated with temperature, organic matter, exopolymer particles, and particulate-attached bacteria; this last accounted for as much as 89.6% of the total abundance. During the rainy season, BP was generally much higher than PP, and values of BP/PP > 20 were registered during high freshwater input, suggesting that under these conditions, bacterial activity was predominantly supported by allochthonous inputs of organic carbon. In addition, BB probably represented the main pathway for the synthesis of high-quality (low C:N) biomass that may have been available to the heterotrophic components of the plankton food web, particularly nanoheterotrophs. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,046.2 mg N pot(-1) at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all resulted in a significant (P < 0.01) correlation between cumulative mineral NH (4) (+) -N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N, microbial C, and ultraviolet absorbance of NaHCO(3) extract at 205 and 260 nm revealed no clear relationship with TNU or cumulative mineral NH (4) (+) -N. Soil C/N ratio, acid KMnO(4)-NH (4) (+) -N, alkaline KMnO(4)-NH (4) (+) -N, phosphate-borate buffer extractable NH (4) (+) -N (PB-NH (4) (+) -N), phosphate-borate buffer hydrolyzable NH (4) (+) -N (PB(HYDR)-NH (4) (+) -N) and hot KCl extractable NH (4) (+) -N (H(KCl)-NH (4) (+) -N) were all significantly (P < 0.05) related to TNU and cumulative mineral NH (4) (+) -N of long-term incubation (> 28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio, which showed the highest correlation with TNU at maturity stage (R = -0.929, P < 0.001) and cumulative mineral NH (4) (+) -N (R = -0.971, P < 0.001). Acid KMnO(4)-NH (4) (+) -N plus native soil NH (4) (+) -N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio.

Abstract  We present trajectory-based estimates of Ozone Depletion Potentials (ODPs) for very short-lived halogenated source gases as a function of surface emission location. The ODPs are determined by the fraction of source gas and its degradation products which reach the stratosphere, depending primarily on tropospheric transport and chemistry, and the effect of the resulting reactive halogen in the stratosphere, which is determined by stratospheric transport and chemistry, in particular by stratospheric residence time. Reflecting the different timescales and physico-chemical processes in the troposphere and stratosphere, the estimates are based on calculation of separate ensembles of trajectories for the troposphere and stratosphere. A methodology is described by which information from the two ensembles can be combined to give the ODPs.

The ODP estimates for a species with a fixed 20 d life-time, representing a compound like n-propyl bromide, are presented as an example. The estimated ODPs show strong geographical and seasonal variation, particularly within the tropics. The values of the ODPs are sensitive to the inclusion of a convective parametrization in the trajectory calculations, but the relative spatial and seasonal variation is not. The results imply that ODPs are largest for emissions from south and south-east Asia during Northern Hemisphere summer and from the western Pacific during Northern Hemisphere winter. Large ODPs are also estimated for emissions throughout the tropics with non-negligible values also extending into northern mid-latitudes, particularly in the summer. These first estimates, whilst made under some simplifying assumptions, show larger ODPs for certain emission regions, particularly south Asia in NH summer, than have typically been reported by previous studies which used emissions distributed evenly over land surfaces.

Abstract  A novel family of hole-transport polyurethanes (PUs) has been developed. The PUs were prepared from the condensation polymerization of isophorone diisocyanate (IPDI) with ( E, E)-1,4-bis(2-hydroxystyryl) benzene, an oligo p-phenylene-(E)-vinylene (OPV) unit, and various amounts of 2,5-bis(4-hydroxyphenyl)- 1,3,4-oxadiazole (OXD), as well as with 4-tert-butyl phenol as the terminal group. The PUs demonstrates superior properties that were concluded on the basis of the improved current injection in the corresponding hole-only device. The OLED device with the OPV-PU interfacial layer inserted in ITO/PEDOT: PSS(20 nm)/ PU(30 nm)/alpha-NPB(10 nm)/Bebq(2)(20 nm)/ Ca(10 nm)/ Ag(100 nm) has a dramatic voltage reduction of 2.5 V under the current density of 100 mA/cm(2). When compared to the control device, the current efficiency was improved 2.37 times. The maximum brightness increased to 14900 cd/m(2) in comparison to that of 5780 cd/m(2) for the control device. The performance of the OLED devices was fine-tuned by adjusting the combination of the OPV and OXD units to reach electron-hole balanced conditions. The maximum current efficiency increased to 4.12 cd/A at 5.5 V when the PU layer of OPV: OXD = 67: 33 was used.

Abstract  The experiment was conducted to evaluate Bio-V-Pro as an alternative protein source in broiler diets. Treatments were control, Bio-V-Pro 1% (BP 1), Bio-V-Pro 3% (BP 3), and Bio-V-Pro 5% (BP 5). During the starter period, all treated groups showed better performance than control group in weight gain and feed intake (p < 0.05). The best FCR was observed in BP 1 group and the worst was found in BP 5 group., For the overall period, chicks fed BP 1 and BP 3 diets gained more than the chicks fed the control and BP 5 diets. All Bio-V-Pro fed groups consumed more feed than the control group (p < 0.05). FCR were similar between the control and BP 1 group, but BP 3 and BP 5 groups showed higher FCR than the control group. During the starter period, all BP groups showed better utilizability of crude protein, crude ash and phosphorus than the control group (p < 0.05). For the finisher period, except for the BP 5 group, the nutrient utilizability was not significantly different in most nutrients. Nutrients utilizability had a tendency (not significant) to decrease as the level of Bio-V-Pro in the diet was increased. Lysine utilizability was not affected by the dietary treatment, however, methionine utilizability was higher in BP 1 and BP 3 group than in the control group. From the results of this experiment, it seems that Bio-V-Pro is a good alternative protein source which can replace fish meal in starter diet up to 3% of the diet effectively.

Abstract  A new light-emissive material, bis(3H-1,2,3-triazolo-[4,5-b]pyridine-3-ol)zinc (Zn(TAP)(2)), has been synthesized and characterized by FT-NMR, FT-IR, UV-Vis, and elemental analysis. The photoluminescence (PL) of Zn(TAP)(2) was measured from the DMF solution at 460 nm. The HOMO (6.5 eV) and LUMO (2.8 eV) energy levels of Zn(TAP)(2) were estimated from the measurement of cyclic voltammetry. The devices with structures of ITO/NPB/Zn(TAP)(2)/LiF/Al and ITO/NPB/Zn(TAP)(2)/Alq(3)/LiF/Al were constructed to investigate their electroluminescent (EL) performance. Zn (TAP)(2) is supposed to be a good emitting material in the EL device.

Abstract  Temperature gradient capillary electrophoresis (TGCE) can be used to distinguish heteroduplex from homoduplex DNA molecules and can thus be applied to the detection of various types of DNA polymorphisms. Unlike most single nucleotide polymorphism (SNP) detection technologies, TGCE can be used even in the absence of prior knowledge of the sequences of the underlying polymorphisms. TGCE is both sensitive and reliable in detecting SNPs, small InDel (insertion/deletion) polymorphisms (IDPs) and simple sequence repeats, and using this technique it is possible to detect a single SNP in amplicons of over 800 bp and 1-bp IDPs in amplicons of approximately 500 bp. Genotyping data obtained via TGCE are consistent with data obtained via gel-based detection technologies. For genetic mapping experiments, TGCE has a number of advantages over alternative heteroduplex-detection technologies such as celery endonuclease (CELI) and denaturing high-performance liquid chromatography (dHPLC). Multiplexing can increase TGCE's throughput to 12 markers on 94 recombinant inbreds per day. Given its ability to efficiently and reliably detect a variety of subtle DNA polymorphisms that occur at high frequency in genes, TGCE shows great promise for discovering polymorphisms and conducting genetic mapping and genotyping experiments.

Abstract  A graded doping technique was introduced to fabricate high brightness and high efficiency OLEDs, in which the luminescent layer consists of the mixture of NPB, Alq3 and an emitting dopant 5,6,11,12-petraphenylnaphthacene (Rubrene), where the concentration of NPB raised while the concentration of Alq(3) was declined gradually in the deposition process. This graded doping device exhibited the maximum emission of 49300cd/m(2) at 35V and the maximum efficiency of about 8cd/A at 10V, respectively, which have been improved by two times in comparison with the conventional doped devices.

Abstract  White light emission is important for full color display and back-lighting applications of organic electroluminescence devices. In the present work, a white light organic electroluminescent device has been fabricated by employing a hole-transporting layer (HTL) of mixed light-emitting organic materials. The device has a structure of glass substrate\indium tin oxide (ITO)\mixed HTL\Tris(acetylacetonato) (monophenanthroline) (Tb(ACAC)(3)Phen)\Mg:Ag. The mixed HTL was prepared by spin coating of a solution of poly(N-vinylcarbazole) (PVK), N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1'-biphenyl-4,4'-diamine (NPB) and 1,1-bis(4-tolylaminophenyl) cyclolexane (TAPC). The Tb complex layer plays several roles in the present device. It is an electron-transporting layer as well as a green light-emitting layer. In addition, it also functions as a hole-blocking layer such that recombination of electrons and holes can also take place in the HTL. Blue and red emissions are due to the NPB and TPAC in the HTL. Together with the green emission from the Tb complex, white light emission above 1000 cd/m(2) has been achieved at a driving voltage of 20 V. (C) 2000 Elsevier Science S.A. All rights reserved.

Abstract  Electrochemically modified indium-tin oxide (ITO) surfaces were used as hole injection electrodes in organic light emitting devices. Substantial improvement in hole injection and electroluminescence efficiencies were observed in devices with the sample configuration of ITO/NPB/Alq(3)/LiF/Al. The turn-on voltage reduced from 5.3 V for device with pristine ITO to 2.8 V for device with ITO pretreated electrochemically at +2.4 V in K4P2O7 electrolyte. The current and power efficiencies at 20 mA/cm(2) were increased correspondingly from 3.0 cd/A and 0.84 lm/W to 3.4 cd/A and 1.24 lm/W. The mechanisms behind this performance enhancement were discussed.

Abstract  A new emitting material, tetra( beta-naphthyl)silane (TNS), was synthesized and used as hole blocking material in organic light-emitting devices (OLEDs). Devices with a configuration of ITO/alpha-NPB/TNS/Alq(3)/Al have been constructed, where ITO is indium-tin-oxide, alpha-NPB is (4,4' -bis[N-(1-naphthyl)-N-phenylamino] biphenyl), and Alq(3) is (8-quinolinolato) aluminum. A high performance blue light OLED was obtained, which emits blue light with a peak at 439 nm and starts to emit light at 6 V and the luminance can reach to 3800 cd/m(2) at 13 V and 250 mA/cm(2). (c) 2004 Elsevier B.V. All rights reserved.

Abstract  The analytical capabilities of an improved mini-XRF instrument for trace element analysis are explored to obtain U-Th-Pb ages. For single monazite grains as small as 50 gm, the detection limits for U, Th and Pb, with counting times of 10 min, are similar to10 ppm; counts collected for 40 min are sufficient to date single monazite grains as young as 15 Ma. The precision of the age data depends essentially on the counting statistics of the main X-ray peak (N-Pb (Lalpha) (1/2)) used to analyze for lead; the age uncertainty is proportional to the age of the grain, the total contents of Th and U, and the (squared) integration time. The reliability of the chemical dating method is tested using monazite separates from amphibolite facies metamorphic monazite samples from the central Alps, for which the chemical ages are compared to mass spectrometric (U-Pb TIMS) ages. We show that populations of analyses obtained using the new instrument on single grains as young as 25-30 Ma agree within error with the TIMS data. For monazite separates with complex age patterns, such as polymetamorphic samples yielding discordant isotopic ages, the statistical analysis of chemical age data, obtained from populations of 26-50 grains, is advantageous in that it may provide additional insight into the reasons for the discordancy. Chemical Th-U-Pb dating of monazite by the XRF method offers considerably improved accuracy and precision, compared with chemical dating by electron microprobe, which typically becomes impractical for samples less than 100-200 Ma in age. Conversely, the minimum grain size required for the new instrument (Phi similar to 50 mum) is well above the spatial ;resolution of the electron microprobe (Phi similar to 2 mum). A companion paper [Scherrer et al., this volume] describes further developments towards microanalysis by XRF, with improved spatial resolution. (C) 2002 Elsevier Science B.V All rights reserved.

Abstract  On the basis of the yellow iridium phosphor, bis(2-phenylbenzothiozolato-N,C-2 ')iridium(acetylacetonate) [(bt)(2)Ir(acac)], the three halogen-substituted analogues were designed and synthesized by introducing the F, Cl, and Br atoms to the 4-position of phenyl ring in the ligand of 2-phenylbenzo[d]thiazole. The optoelectronic properties of all the four iridium complexes were fully investigated. Compared to the 559 nm peak emission of (bt)(2)Ir(acac) in CH2Cl2 solution, adding F atom caused the peak emission of (4-F-bt)(2)Ir(acac) blue shift to 540 nm, while adding Cl and Br atoms made the peak emissions of (4-Cl-bt)(2)Ir(acac) and (4-Br-bt)(2)Ir(acac) slightly blue shift to 554 and 555 nm, respectively. The PhOLEDs using the four iridium complexes as dopants were initially fabricated in the conventional device structure (device I): ITO/MoO3/NPB/CBP/CBP:dopants/TPBi/LiF/Al. The three halogen-substituted analogues exhibited turn-on voltages of 3.5-3.9 V, maximum current efficiencies of 35.5-52.4 cd A(-1), maximum power efficiencies of 18.3-29.4 lm W-1 and maximum external quantum efficiencies (EQE) of 12.1-17.3%, which were superior than the (bt)(2)Ir(acac)-based device (28.4 cd A(-1), 19.9 lm W-1, 9.8%). After reducing the hole-injecting barrier and using better carrier-transporting materials in the optimized device II, ITO/MoO3/TAPC/TCTA/CBP:dopants/TmPyPB/LiF/Al, all the four devices exhibited lower turn-on voltages of 2.9-3.1 V and excellent performance with maximum EQE over 20%. As a result, they showed high power efficiencies in the range of 55.9-83.2 lm W-1. Among the four optimized devices, the (4-F-bt)(2)Ir(acac)-based device achieved the highest power efficiency of 83.2 lm W-1. Remarkably, the (bt)(2)Ir(acac)-based device still possessed high current efficiency of 53.5 cd A(-1), power efficiency of 23 lm W-1, and EQE of 19.6% at extremely high luminance of 10 000 cd m(-2).