Solution electrochemical studies have been conducted of the principle lumophores, dopants, and hole-transport agents of aluminum-quinolate(Alq3)-based organic light-emitting diodes (OLEDs) along with the characterization of their electrogenerated chemiluminescence (ECL). In acetonitrile/benzene solvent mixtures, Alq3 shows single one-electron reduction and oxidation processes, with a separation between the first oxidation and first reduction potentials, ΔE electrochemical = 3.03 V, close to the estimates of energy difference between HOMO and LUMO levels obtained from absorbance spectra of thin films of Alq3, ΔE optical = 3.17 eV. A new sulfonamide derivative of Alq3, (Al(qs)3), showed a positive shift (ca. 0.32 V) in the first reduction potential versus the parent molecule, and resolution of the overall reduction process into three successive, chemically reversible, one-electron reductions. Two successive one-electron oxidations are seen for 4,4‘-bis(m-tolyphenylamino)biphenyl (TPD), a hole-transporting material in many bilayer OLEDs, and for TPDF2, a fluorinated version of TPD, with TPDF2 oxidation occurring 0.1 V positive of that for TPD. Electrogenerated chemiluminescence reactions (Alq3 -•/TPD+• (or TPDF2 +•) and Al(qs)3 -•/TPD+• (or TPDF2 +•)) were found to produce emission spectra from Alq3*s or Al(qs)3*s states which were nearly identical to those seen from OLEDs based upon these molecules. Emission intensities increased with the increasing potential difference between the relevant redox couples. The diisoamyl derivative of quinacridone (DIQA), a quinacridone dopant for certain Alq3-based OLEDs, undergoes two successive one-electron reductions and two successive one-electron oxidations. The ECL reactions DIQA-•/DIQA+•, DIQA+•/Alq3 -•, DIQA+•/Al(qs)3 -•, DIQA-•/TPD+• and DIQA-•/TPDF2 +• all produce the same singlet emissive state, DIQA*s, and the same emission spectral response seen in quinacridone and DIQA-doped OLEDs.

A soluble derivative of quinacridone, N,N′-di-isoamyl quinacridone (DIQA), has been synthesized and used to study the mechanisms of Förster energy transfer and charge transfer in organic light-emitting diodes (OLEDs) based on 8-hydroxyquinoline (Alq3). Quantum efficiencies and spectra were measured for both photoluminescence (PL) and electroluminescence (EL) for films of poly(9-vinylcarbazole) (PVK) doped with Alq3 and DIQA. Both PL and EL showed an efficiency enhancement in films of PVK:Alq3:DIQA compared to films of PVK:Alq3. However, the optimal DIQA doping concentration was found to be lower for EL than for PL. Examination of the spectra revealed that more emission originated from DIQA for EL than for PL at a given doping level. We conclude that Förster energy transfer from Alq3 to DIQA occurs in both cases of PL and EL, but that charge transfer to DIQA occurs in the operation of the OLED resulting in additional pathways to DIQA emission. Ultraviolet photoelectron spectroscopy measurements showed that electron transfer from Alq3 to DIQA, hole transfer from PVK to DIQA, and hole transfer from Alq3 to DIQA are all energetically favorable processes. These results suggest that charge transfer is an important mechanism in the efficiency enhancement seen in OLEDs based on a host–dopant scheme, and that both the electronic properties and the optical properties of the dopant material are important parameters for device optimization.

A blood culture cohort study investigating issues related to isolation of coagulase-negative staphylococci (CoNS) and other skin microflora is reported. Data were collected over 12 weeks to determine the incidence of significant CoNS bacteremia versus that of pseudobacteremia (contaminants) and to evaluate drug therapy in patients with cultures positive for CoNS. In addition, the effectiveness of 0.2% chlorine peroxide as a bactericidal disinfectant was compared to that of 10% providone iodine. A total of 3,276 cultures of blood from 1,433 patients were evaluated in the study. Eighty-nine cultures were positive for skin flora, with 81 of 89 (91%) involving CoNS. The incidence of significant CoNS bacteremia was 20 of 81 (24.7%), that of indeterminate bacteremia was 10 of 81 (12.3%), and that of contamination was 59 of 81 (72.8%). The incidence of significant bacteremia involving CoNS was double the 10 to 12% rate based on previous estimations at our institutions. In tests with the two bactericidal disinfectants, 22 of 1,639 cultures (1.3%) in the chlorine peroxide group versus 37 of 1,637 (2.3%) in the providone iodine group were considered contaminated (P = 0.065). Rates of contamination for venipuncture versus catheter collection were not significantly different (P = 0.46). The overall contamination rate was 59 of 3,276 (1.8%), which is consistent with the lower end of published quality assurance benchmark standards. The low rate was believed to be due to the professional phlebotomy staff in our institutions. There was excellent agreement between retrospective analysis by reviewers, when formal criteria were used, and the attending physicians’ intuitive clinical impressions in the classification of significant bloodstream infections (100% agreement) or contamination (95% agreement). However, physicians still used antimicrobial agents to treat nearly one-half of the patients with contaminated blood cultures, with vancomycin being misused in 34% of patients. In addition, 10% of patients with significant bacteremia were treated with inappropriate agents. There were no significant adverse events or prolonged hospital stays due to the unnecessary use of vancomycin; however, the additional costs of treating patients whose cultures contained CoNS contaminants was estimated to be $1,000 per patient. Measures to limit the unnecessary use of vancomycin (and other agents) are important.

primary colors by varying the size of the arrays of metal nanoparticles (width, length), or by using different metals. A more detailed study concerning color tuning of these films by selecting proper materials and processing conditions will be presented separately. ExperimentalColloidal silver particles with a surface layer of dodecanethiol were synthesized according to slightly modified versions of methods reported in the literature [20,21]. Silver trifluoromethanesulfonate (CF 3 SO 3 Ag, 9 × 10 ±4 mol), tetraoctylammonium bromide ([C 8 H 17 ] 4 NBr, 4 × 10 ±3 mol), and 1-dodecanethiol (C 12 H 25 SH, 1.8 × 10 ±3 mol) were dissolved in 80 mL of toluene. A freshly prepared aqueous sodium borohydride solution (1 × 10 ±2 mol in 25 mL of distilled water) was slowly added under vigorous stirring. The organic layer was separated, and the solution was concentrated by solvent evaporation to a volume of approximately 5 mL. Then, 500 mL of ethanol was added at ±20 C. After sedimentation of the particles, the outstanding solution was decanted, and the residue was again treated with 500 mL of ethanol at ±20 C. Finally, the particles were dried for 12 h at room temperature and under reduced pressure.TGA was performed with a Netzsch TG 209 instrument. The nanoparticles (ca. 10 mg) were heated under a nitrogen flow at a rate of 10 C/min to 600 C.TEM was performed using a Philips EM 301 electron microscope. A drop of the toluene reaction mixture containing the colloidal metal particles was placed onto a carbon film supported by a copper grid. After evaporation of the solvent, the samples were inserted into the electron microscope. The undrawn and drawn polyethylene/silver nanocomposites (containing 4 wt.-% nanoparticles) were cut at low (±80 C) temperatures using a diamond knife; the thin slices were collected on a copper grid and used for TEM.Polarized UV-vis spectra were recorded with a Perkin-Elmer Lambda 900 instrument, fitted with motor-driven Glan±Thomson polarizers. The nanocomposites were sandwiched between two quartz glass slides and coated with a small amount of silicone oil in order to minimize light scattering at the film surfaces [22].

We show that the leading chiral corrections to the AS= 1 f, vector form factors of hyperons are 0 (m, ) and O(mj'*), and are expected to be -20-30 % by dimensional analysis. This is consistent with the Ademollo-Gatto theorem. We compute the O(m,) corrections and a subset of the O(mg") corrections using an effective Lagrangian in which the baryons are treated as heavy particles. All of these corrections are surprisingly small, -5%; combining them, we obtain -5-10 7% corrections. The pattern of corrections is very different from that predicted by quark models.PACS number(s1: 13.30. Ce, 11.30.Rd, 14.20.Gk, 14.20.Jn I. INTRODUCTIONIn this paper we consider the application of chiral perturbation theory to the f vector form factor of octet baryon states. The form factors of the vector current are conventionally defined by where q ~p , -p , . Our interest in the form factor f is due to the fact that it is important for semileptonic hyperon decays, which in turn are used to determine Vu, [I].It is often assumed that SU(3bbreaking corrections to f, are ~( m ? ) and small due to the Ademollo-Gatto (AG) theorem [2]. Indeed, nonrelativistic quark model and bag model calculations of SU(3)-breaking corrections to f , typically give corrections of order 1 % [3]. In the SU(3) limit mu = m d = m , , the vector form factors at zero-momentum transfer are simply Clebsch-Gordan coefficients, while the axial form factors are simple linear combinations of two parameters D and F. (Be-