The use of a single ammonium acidic salt towards simple green co-precipitation synthesis for Mn4+-activated fluorides.

Herein, a simple green co-precipitation route for Mn4+-activated fluorides has been realized via individually using the aqueous acidic salt NH4HF2 as a solvent. The systematic explorations of ionization, erosion, solvent concentration, solvency on reactants, and reaction with an extra weak acid disclosed that the near-saturated aqueous NH4HF2, ionizing into abundant HF2-, H+, and F- ions, exhibited large dissolving capacity and good stabilization on Mn4+ without obvious toxicity. The green synthesized example of Cs2GeF6:Mn4+ emitted a typical narrow band red light at 633 nm with normal optimal doping at ∼8 at%. Compared with its contrast prepared from the HF system, it experienced only ∼10% reduction in quantum efficiency and slight emission attenuation below 150 °C as the more humidity-sensitive weaker acid surface aroused lattice thermal vibration. The further action as red component fabricated a high-quality warm white light-emitting diode (W-LED) with a high color rendering index (Ra ∼ 91), high luminous efficacy (∼149 lm W-1), low correlated color temperature (∼3211 K), and good color stability against the operating environment. Combined with the universal synthesis of A2XF6:Mn4+ (A = K, Rb, Cs; X = Si, Ge), our findings can probably open up a simple and feasible green synthetic strategy for efficient Mn4+-doped fluorides using acidic salts.

Luminescence properties and warm white LED application of a ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ .

Herein, a Mn4+ ion doped complex ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ has been synthesized through a facile two-step co-precipitation method at room temperature. The crystal structure, morphological properties and influence of the dopant concentration, temperature and humidity on luminescence properties as well as the performance of the as-synthesized phosphor used in white light emitting diodes (WLEDs) were investigated carefully. Intense absorption in the blue region (∼460 nm) and bright narrow-band red emission (∼630 nm) with high color purity were observed from this resultant powder. Temperature-dependent investigation and reliability examination in a HTHH environment (85 °C high temperature and 85% high humidity) indicate that the obtained ternary-alkaline fluoride phosphor K2NaAlF6:Mn4+ presents more exceptional thermal quenching behavior and longevity compared to some other binary-alkaline fluorides. Moreover, using K2NaAlF6:Mn4+ as a red light component, a warm WLED with a preferable color rendering index (Ra = 85.5) and luminous efficacy (LE = 91.2 lm W-1) as well as a low corresponding color temperature (CCT = 3650 K) is easily achieved, further revealing the great potential of the as-prepared ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ for WLED applications.

Emergence of Panton-Valentine leucocidin-positive ST8-methicillin-resistant Staphylococcus aureus (USA300 clone) in Korea causing healthcare-associated and hospital-acquired bacteraemia.

Panton-Valentine leucocidin (PVL)-positive sequence type (ST)8-MRSA-SCCmec IVa (USA300) is the epidemic strain of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in North America. USA300 is extremely rare in South Korea, and PVL-negative ST72 SCCmec type IVc is the predominant CA-MRSA clone. In a multicentre, prospective cohort study of S. aureus bacteraemia, we identified PVL-positive ST8-MRSA isolates by performing multilocus sequence typing and PCR for PVL. We analyzed the clinical characteristics of patients with PVL-positive ST8-MRSA bacteraemia, and performed SCCmec, spa, and agr typing, PCR for arginine catabolic mobile element (ACME), virulence gene profiling, and pulsed-field gel electrophoresis (PFGE). Among a total of 818 MRSA isolates, we identified ten isolates of PVL-positive ST8-MRSA (USA300) (3 from Hospital D, 4 from Hospital G, and 3 from Hospital A), all of which involved exclusively healthcare-associated (5 isolates) and hospital-acquired bacteraemia (5 isolates). This strain accounted for 8~10 % of the hospital-acquired MRSA bacteraemia in Hospitals D and G. Bacteraemia of unknown origin was the most common type of infection followed by pneumonia. All the isolates were SCCmec type IVa, spa type t008, and agr group I. Eight of the isolates harboured ACME. In a PFGE analysis, four isolates were identical to the USA300 control strain, five differed by a single band, and the remaining one differed by two bands. All the isolates were pulsed-field type USA300. This is the first report of healthcare-associated and hospital-acquired bacteraemia caused by USA300 in South Korea. USA300 seems to be an emerging hospital clone in this country.

Mesoporous nanoparticles Gd2O3@mSiO2/ZnGa2O4:Cr3+,Bi3+ as multifunctional probes for bioimaging.

Red/near infrared (NIR) persistent luminescent nanoparticles (PLNPs) hold great potential as a new generation of probes for the detection and imaging of biomolecules. Based upon the consideration that a single nanoprobe could serve multiple purposes, the development of a multimodal nanoprobe that combined the properties of rechargeable persistent emitting luminescence, magnetic resonance imaging (MRI) and drug delivery has attracted our attention as a promising prospect in the field of nanotechnology directed toward biomedical applications. Herein, Gd2O3@mSiO2/ZnGa2O4:Cr3+,Bi3+ (ZGOCB) mesoporous nanoparticles that exhibit enhancement of red (∼695 nm) persistent luminescence (∼18 d) properties were synthesized by using mesoporous silica nanospheres both as morphology-controlling templates and vessels. Being composed of hybrid shell/core architecture and through surface functionalization, Gd2O3@mSiO2/ZGOCB mesoporous nanoparticles possess the capacity for in vivo and in situ real-time monitoring, targeting tumors and drug delivery. Simultaneously, Gd2O3@mSiO2/ZGOCB exhibits a prominent longitudinal relaxivity, indicating that these nanoparticles could also be used as magnetic resonance imaging agents. We believe that this rechargeable red persistent luminescence and MRI-based core/shell structure of the multimodal nanoprobe offers a promising nano-platform for both diagnostics and therapeutics of reactive species in living cells or in vivo.

A yellow-emitting phosphor of Mn(2+)-doped Na2CaP2O7.

A yellow-emitting Na2CaP2O7:Mn(2+)phosphors have been synthesized by solid state reaction. The crystal structure, photoluminescence properties as well as concentration quenching mechanism have been investigated. The (4)T1-(6)A1 emission of Mn(2+)in Na2CaP2O7 phosphor ranges from 500 to 650 nm and exhibits a red shift while increasing the Mn(2+)concentration. The crystal field strength is calculated based on the combination of excitation spectrum and Tanabe-Sugano diagram. The chromaticity coordinates of Na2CaP2O7:Eu(2+), Mn(2+)phosphors were discussed in order to develop the potential application in white light-emitting diodes (LEDs).

Clinical implication of extended-spectrum cephalosporin nonsusceptibility in Streptococcus pneumoniae meningitis.

The clinical implication of extended-spectrum cephalosporin (ESC) resistance has been unclear in patients with Streptococcus pneumoniae meningitis (SPM). We collected the clinical data of 120 patients with SPM in 12 hospitals of the Republic of Korea. The clinical characteristics and outcomes of 23 ESC-nonsusceptible SPM episodes were compared to those of 97 ESC-susceptible episodes. Hospital acquisition, presence of other foci of pneumococcal infection, septic shock at initial presentation, or concomitant bacteremia were more commonly observed in ESC-nonsusceptible than ESC-susceptible SPM. Empiric antimicrobial therapy with vancomycin and ESC combination was very common in both groups. Although there was a tendency towards higher early fatality in ESC-nonsusceptible SPM (3-day mortality; 17.4 % vs. 4.4 %, p = 0.05), in-hospital mortality (26.1 % vs. 20.9 %, p = 0.59) and median length of hospital stay (20 days vs. 24 days, p = 0.34) did not differ between ESC-nonsusceptible and ESC-susceptible SPM.

Development of bacteraemia or fungaemia after removal of colonized central venous catheters in patients with negative concomitant blood cultures.

There are limited data on the clinical significance of positive central venous catheter (CVC) tip cultures associated with concomitant negative blood cultures performed at the time of CVC removal. A retrospective cohort study of all patients who yielded isolated positive CVC tip cultures was conducted in a tertiary-care hospital with 2200 beds during a 10-year period. All patients with isolated positive CVC tip cultures were observed for the development of subsequent bacteraemia or fungaemia between 2 and 28 days after CVC removal. An isolated positive CVC tip culture was defined as a case in which (i) a CVC tip culture yielded > or = 15 colonies using a semiquantitative culture method and (ii) at least two sets of blood samples revealed no organism at, or close to, the time of CVC removal (48 h before to 48 h after CVC removal). During the study period, 312 patients with isolated positive CVC cultures were enrolled. Eight (2.6%; 95% CI 1.2-5.1) of the 312 patients yielding isolated bacterial or fungal CVC tip cultures developed subsequent bloodstream infection (BSI) caused by the same species as that isolated from the tip culture (Staphylococcus aureus, 1: Enterococcus spp.; 2: Pseudomonas aeruginosa; and 3: Candida spp.). Among 125 patients from whose CVC tips the above four organisms were grown, seven (12.3%) of 57 patients who did not receive appropriate antibiotic therapy within 48 h after CVC removal subsequently developed BSI, but only one (1.5%) of 68 patients who did receive appropriate therapy developed BSI (OR 0.11, p 0.02).

Modulation of Nad(P)H:quinone oxidoreductase (NQO1) activity mediated by 5-arylamino-2-methyl-4,7-dioxobenzothiazoles and their cytotoxic potential.

Synthesized 5-arylamino-2-methyl-4,7-dioxobenzothiazoles 3a-3o were evaluated for modulation of NAD(P)H: quinone oxidoreductase (NQO1) activity with the cytosolic fractions derived from cultured human lung cancer cells and their cytotoxicity in cultured several human solid cancer cell lines. The 4,7-dioxobenzothiazoles affected the reduction potential by NQO1 activity and showed a potent cytotoxic activity against human cancer cell lines. The tested compounds 3a, 3b, 3g, 3h, 3n and 3o were considered as more potent cytotoxic agents, and comparable modulators of NQO1 activity.