Spleen tyrosine kinase/FMS-like tyrosine kinase-3 inhibition in relapsed/refractory B-cell lymphoma, including diffuse large B-cell lymphoma: updated data with mivavotinib (TAK-659/CB-659).

We report an updated analysis from a phase I study of the spleen tyrosine kinase (SYK) and FMS-like tyrosine kinase 3 inhibitor mivavotinib, presenting data for the overall cohort of lymphoma patients, and the subgroup of patients with diffuse large B-cell lymphoma (DLBCL; including an expanded cohort not included in the initial report). Patients with relapsed/refractory lymphoma for which no standard treatment was available received mivavotinib 60-120 mg once daily in 28-day cycles until disease progression/unacceptable toxicity. A total of 124 patients with lymphoma, including 89 with DLBCL, were enrolled. Overall response rates (ORR) in response-evaluable patients were 45% (43/95) and 38% (26/69), respectively. Median duration of response was 28.1 months overall and not reached in DLBCL responders. In subgroups with DLBCL of germinal center B-cell (GCB) and non-GCB origin, ORR was 28% (11/40) and 58% (7/12), respectively. Median progression free survival was 2.0 and 1.6 months in the lymphoma and DLBCL cohorts, respectively. Grade ≥3 treatment-emergent adverse events occurred in 96% of all lymphoma patients, many of which were limited to asymptomatic laboratory abnormalities; the most common were increased amylase (29%), neutropenia (27%), and hypophosphatemia (26%). These findings support SYK as a potential therapeutic target for the treatment of patients with B-cell lymphomas, including DLBCL. Trial registration: ClinicalTrials.gov number: NCT02000934.

Evolution of fluoroquinolone-resistant Escherichia coli in the gut after ciprofloxacin treatment.

BACKGROUND: Three healthy volunteers carried similar quinolone-resistant E. coli (QREC) (pulsed field gel electrophoresis profiles) in their gut before and after 14 days ciprofloxacin treatment. Given the intensity of the selective pressure and the mutagenic properties of quinolones, we determined whether these strains had evolved at the phenotypic and/or genomic levels. MATERIAL AND METHODS: Commensal QREC from before day-0 (D0), and a month after 14 days of ciprofloxacin (D42) were compared in 3 volunteers. Growth experiments were performed; acetate levels, mutation frequencies, quinolone MICs and antibiotic tolerance were measured at D0 and D42. Genomes were sequenced and single nucleotide polymorphisms (SNPs) between D0 and D42 were analyzed using DiscoSNP and breseq methods. Cytoplasmic proteins were extracted, HPLC performed and proteins identified using X!tandem software; abundances were measured by mass spectrometry using the Spectral Counting (SC) and eXtraction Ion Chromatograms (XIC) integration methods. RESULTS: No difference was found in MICs, growth characteristics, acetate concentrations, mutation frequencies, tolerance profiles, phylogroups, O-and H-types, fimH alleles and sequence types between D0 and D42. No SNP variation was evidenced between D0 and D42 isolates for 2/3 subjects; 2 SNP variations were evidenced in one. At the protein level, very few significant protein abundance differences were identified between D0 and D42. CONCLUSION: No fitness, tolerance, metabolic or genomic evolution of commensal QREC was observed overtime, despite massive exposure to ciprofloxacin in the gut. The three strains behaved as if they had been unaffected by ciprofloxacin, suggesting that gut may act as a sanctuary where bacteria would be protected from the effect of antibiotics and survive without any detrimental effect of stress.

Dimercaptosuccinic acid in combination with carbapenems against isogenic strains of Escherichia coli producing or not producing a metallo-ß-lactamase in vitro and in murine peritonitis.

BACKGROUND: Carbapenemase-producing Enterobacterales represent a major therapeutic challenge. MBLs, requiring zinc at their catalytic site, could be inhibited by meso-dimercaptosuccinic acid (DMSA), a heavy metal chelator already widely used for treating lead intoxication. OBJECTIVES: To evaluate the activity of carbapenems alone or combined with DMSA against MBL-producing Escherichia coli in a severe murine peritonitis model. METHODS: Isogenic strains of wild-type E. coli CFT073 producing the MBLs NDM-1, VIM-2 and IMP-1, and the control serine carbapenemases OXA-48 and KPC-3 were constructed. MIC determinations and time-kill assays were performed for imipenem, meropenem and ertapenem alone or in combination with DMSA. Infected mice were treated intraperitoneally for 24 h with imipenem, DMSA or their combination. Bacterial counts in peritoneal fluid and spleen were assessed at 24 h. RESULTS: DMSA in combination with each carbapenem caused a significant decrease in the MICs for all MBL-producing strains, in a concentration-dependent manner, but did not provide benefit against non-MBL strains. In mice infected with the NDM-1-producing strain, the combination of imipenem and DMSA significantly reduced bacterial counts in peritoneal fluid (P = 0.0006) and spleen (P < 0.0001), as compared with imipenem alone, with no benefit against the KPC-3-producing and CFT073 strains. DMSA concentrations in plasma of mice were comparable to those obtained in humans with a standard oral dose. CONCLUSIONS: DMSA restores the activity of carbapenems against MBL-producing strains, and its combination with carbapenems appears to be a promising strategy for the treatment of NDM-producing E. coli infections.

Expression of CTX-M-15 limits the efficacy of ceftolozane/tazobactam against Escherichia coli in a high-inoculum murine peritonitis model.

OBJECTIVES: Among carbapenem-sparing therapies, ceftolozane/tazobactam has been proposed for the treatment of infections due to CTX-M-15-producing Escherichia coli. However, few data exist on its in vivo activity in infections associated with a high bacterial inoculum. METHODS: We analysed ceftolozane/tazobactam activity against susceptible E. coli CFT073-RR and its CTX-M-15-producing transconjugant E. coli CFT073-RR Tc blaCTX-M-15, in vitro at low and high inocula, and in a high-inoculum murine model of peritonitis. RESULTS: Against E. coli CFT073-RR Tc blaCTX-M-15, ceftolozane/tazobactam bactericidal effect was impaired in vitro with only a minor inoculum effect; this translated into reduced activity compared with imipenem in the mouse peritonitis model. CONCLUSIONS: Combination of extended spectrum ß-lactamase expression and high inoculum size may be a clinical situation at risk of reduced bactericidal activity of ceftolozane/tazobactam.

The inoculum effect of Escherichia coli expressing mcr-1 or not on colistin activity in a murine model of peritonitis.

OBJECTIVES: Colistin often remains the last resort antibiotic active against carbapenemase-producing Enterobacteriaceae. However, while in vitro inoculum effect has been reported, therapeutic relevance of this phenomenon remains questioned. METHODS: Ten E. coli strains were used that included the wild-type CFT073 and its transconjugant CFT073-MCR-1 and eight susceptible clinical isolates. Mice with peritonitis were treated for 24 h with colistin sulfate. Bacterial loads were determined in peritoneal fluid (PF) and spleen and colistin-resistant mutants were detected. RESULTS: MICs of colistin against the eight susceptible clinical strains and CFT073 ranged from 0.125 to 0.5 mg/L with an inoculum of 105 CFU/mL and from 2 to 4 mg/L with a 107 CFU/mL inoculum; 5/9 strains with an MIC of 4 mg/L were considered resistant according to EUCAST breakpoint (resistance, > 2 mg/L). When the bacterial load of wild-type CFT073 inoculated in mice increased from 107 to 108 CFU: i) mean log10 CFU reduction generated by colistin in PF and spleen decreased from 5.8/mL and 3.1/g, respectively, (p < 0.01) to 0.9/mL and 0.8/g, respectively (NS); ii) mice survival rate decreased from 15/15 (100%) to 6/15 (40%) (p = 0.017); and iii) proportion of mice with selection of colistin-resistant mutants increased from 4/15 to 15/15 (p < 0.01). These results were comparable to those obtained when peritonitis was produced with a 107 CFU bacterial load of E. coli CFT073 expressing mcr-1, for which the mean log10 CFU reductions were 3.5/mL and 0.6/g in PF and spleen, respectively (NS), and survival rate was 8/15 (53%) (p < 0.01 versus survival of mice infected with wild-type CFT073). CONCLUSIONS: Phenotypic colistin resistance in wild-type E. coli due to an increase in inoculum size had a therapeutic impact in mice with peritonitis that was comparable to that observed when the mcr-1 gene was expressed.

Activity of fosfomycin alone or combined with temocillin in vitro and in a murine model of peritonitis due to KPC-3- or OXA-48-producing Escherichia coli.

Background: Alternative therapeutic regimens are urgently needed against carbapenemase-producing Enterobacteriaceae. Fosfomycin often remains active against KPC and OXA-48 producers, but emergence of resistance is a major limitation. Our aim was to determine whether the association of temocillin with fosfomycin might be useful to treat KPC- or OXA-48-producing Escherichia coli infections. Methods: Isogenic derivatives of E. coli CFT073 with blaKPC-3- or blaOXA-48-harbouring plasmids (named CFT073-KPC-3 and CFT073-OXA-48, respectively) were used. The addition of temocillin to fosfomycin was tested using the chequerboard method and time-kill curves as well as in a fatal peritonitis murine model. Mice were treated for 24 h with fosfomycin alone or in combination with temocillin. Bacterial loads, before and after treatment, were determined in the peritoneal fluid and fosfomycin-resistant mutants were detected. Results: Temocillin MICs were 8, 32 and 256 mg/L for CFT073 (WT), CFT073-KPC-3 and CFT073-OXA-48, respectively. Fosfomycin MIC was 0.5 mg/L for all strains. The chequerboard experiments demonstrated synergy for all three strains. In time-kill curves, combining temocillin with fosfomycin was synergistic, bactericidal and prevented emergence of resistance for CFT073-pTOPO and CFT073-KPC-3, but not CFT073-OXA-48. In vivo, for the three strains, bacterial counts were lower in peritoneal fluid with the combination compared with fosfomycin alone (P < 0.001) and inhibited growth of resistant mutants in all cases. Conclusions: The combination of fosfomycin and temocillin demonstrated a benefit in vitro and in vivo against E. coli strains producing KPC-3 or OXA-48-type carbapenemases. This combination prevented the emergence of fosfomycin resistance and proved to be more bactericidal than fosfomycin alone.

The polyol process: a unique method for easy access to metal nanoparticles with tailored sizes, shapes and compositions.

After about three decades of development, the polyol process is now widely recognized and practised as a unique soft chemical method for the preparation of a large variety of nanoparticles which can be used in important technological fields. It offers many advantages: low cost, ease of use and, very importantly, already proven scalability for industrial applications. Among the different classes of inorganic nanoparticles which can be prepared in liquid polyols, metals were the first reported. This review aims to give a comprehensive account of the strategies used to prepare monometallic nanoparticles and multimetallic materials with tailored size and shape. As regards monometallic materials, while the preparation of noble as well as ferromagnetic metals is now clearly established, the scope of the polyol process has been extended to the preparation of more electropositive metals, such as post-transition metals and semi-metals. The potential of this method is also clearly displayed for the preparation of alloys, intermetallics and core-shell nanostructures with a very large diversity of compositions and architectures.

Biological cost of fosfomycin resistance in Escherichia coli in a murine model of urinary tract infection.

Prevalence of fosfomycin resistance in E. coli clinical isolates from UTIs remains very low. Our hypothesis was that fosfomycin resistance may be associated with a biological cost. Three groups of strains of E. coli belonging to the B2 phylogenetic group were used: clinical wild-type (WT) isolates, clinical multidrug-resistant isolates and in vitro fosfomycin-resistant derivatives from the uropathogen clinical strain E. coli CFT073. In each group fosfomycin-susceptible and -resistant isolates were compared. In vitro, we found a significantly decreased growth rate for fosfomycin-resistant strains as compared with susceptible strains in the WT group. In a murine model of ascending UTI, there was a significant reduction in infection rates with fosfomycin-resistant isolates as compared with susceptible ones, in all 3 study groups, ranging from 28 to 39% (P<0.03). All fosfomycin-susceptible clinical strains were virulent in vivo (13/13), while fosfomycin-resistant clinical strains were either virulent (2/7) or non-virulent (5/7) (P<0.002). This difference was not explained by the number of virulence factors or pathogenicity-associated islands. In conclusion, fosfomycin resistance appears to carry some biological cost in E. coli, which may explain in part the apparent paradox of the low prevalence of fosfomycin resistance despite a high rate of spontaneous mutants.

Activity of temocillin in a lethal murine model of infection of intra-abdominal origin due to KPC-producing Escherichia coli.

OBJECTIVES: Temocillin is a 6-α-methoxy derivative of ticarcillin that shows in vitro activity against Enterobacteriaceae producing Klebsiella pneumoniae carbapenemase (KPC). Our objective was to assess in vivo temocillin activity against KPC-producing Escherichia coli. METHODS: Isogenic derivatives of the WT E. coli CFT073 producing KPC-2, KPC-3 or OXA-48 were constructed. An experimental murine model of intra-abdominal infection with sepsis was used. Mice were treated subcutaneously with temocillin 200 mg/kg every 2 h for 24 h, reproducing the duration of time that the free serum concentration of temocillin exceeded the MIC in humans with a regimen of 2 g every 12 h or 2 g every 8 h. Blood, peritoneal fluid (PF) and spleen were collected; 24 h survival and sterility rates were assessed. RESULTS: Temocillin MICs were 8, 16, 32, and 256 mg/L for the susceptible strain and KPC-2-, KPC-3-, and OXA-48-producing strains, respectively. In mice treated with temocillin, significant bacterial reduction was obtained in PF, blood, and spleen for the susceptible strain and KPC-2- and KPC-3-producing strains (P < 0.001) but not for the OXA-48-producing strain. Sterility rates in PF were 53%, 10%, 0% and 0% (P < 0.001) and sterility rates in blood were 77%, 40%, 3% and 0% (P < 0.001), while survival rates were 97%, 97%, 57%, 0% (P < 0.001) for mice infected with the susceptible strain and KPC-2-, KPC-3- and OXA-48-producing strains, respectively. CONCLUSIONS: In a lethal-infection model with bacteraemia from intra-abdominal origin, temocillin retained significant activity in PF, blood and spleen and prevented death in mice by effectively working against KPC-producing E. coli with temocillin MICs ≤16 mg/L.

Impact of a short exposure to levofloxacin on faecal densities and relative abundance of total and quinolone-resistant Enterobacteriaceae.

Emergence of resistant Enterobacteriaceae in the intestinal microbiota during antibiotic treatment is well documented but its early dynamic is not. Here, we compared the densities of total Enterobacteriaceae and relative abundance (RA) of quinolone-resistant Enterobacteriaceae (QRE) in the first stool passed by patients who had a short exposure to levofloxacin (levofloxacin, n=12) or not (control, n=8). Mean densities (SD) (log CFU/g stool) of total Enterobacteriaceae were lower in the levofloxacin group than in the control group-3.4 (1.6) versus 6.7 (1.7), respectively, p <0.001. Conversely, mean RA (SD) of QRE was significantly higher in the levofloxacin group than in the control group-49.7% (23.4) versus 0.1% (3.2), respectively, p <0.05). In conclusion, even a short exposure to levofloxacin has a profound impact on the densities of total Enterobacteriaceae and the QRE-RA.

Cefotaxime and Amoxicillin-Clavulanate Synergism against Extended-Spectrum-ß-Lactamase-Producing Escherichia coli in a Murine Model of Urinary Tract Infection.

We investigated the efficacies of cefotaxime (CTX) and amoxicillin (AMX)-clavulanate (CLA) (AMC) against extended-spectrum-ß-lactamase (ESBL)-producing Escherichia coli in vitro and in a murine model of urinary tract infection (UTI). MICs, the checkerboard dilution method, and time-kill curves were used to explore the in vitro synergism between cefotaxime and amoxicillin-clavulanate against two isogenic E. coli strains-CFT073-RR and its transconjugant, CFT073-RR Tc bla(CTX-M-15)-harboring a bla(CTX-M-15) plasmid and a bla(OXA-1) plasmid. For in vivo experiments, mice were separately infected with each strain and treated with cefotaxime, amoxicillin, and clavulanate, alone or in combination, or imipenem, using therapeutic regimens reproducing time of free-drug concentrations above the MIC (fT≥MIC) values close to that obtained in humans. MICs of amoxicillin, cefotaxime, and imipenem were 4/>1,024, 0.125/1,024, and 0.5/0.5 mg/liter, for CFT073-RR and CFT073-RR Tc bla(CTX-M-15), respectively. The addition of 2 mg/liter of clavulanate (CLA) restored the susceptibility of CFT073-RR Tc bla(CTX-M-15) to CTX (MICs of the CTX-CLA combination, 0.125 mg/liter). The checkerboard dilution method and time-kill curves confirmed an in vitro synergy between amoxicillin-clavulanate and cefotaxime against CFT073-RR Tc bla(CTX-M-15). In vivo, this antibiotic combination was similarly active against both strains and as effective as imipenem. In conclusion, the cefotaxime and amoxicillin-clavulanate combination appear to be an effective, easy, and already available alternative to carbapenems for the treatment of UTI due to CTX-M-producing E. coli strains.

Activity of temocillin in a murine model of urinary tract infection due to Escherichia coli producing or not producing the ESBL CTX-M-15.

OBJECTIVES: Temocillin is a 6α-methoxy derivative of ticarcillin that is resilient to ESBLs. Prospective data about its in vivo activity remain scarce. Our aims were: (i) to evaluate the activity of temocillin in a urinary tract infection (UTI) model due to ESBL-producing Escherichia coli and compare it with that of imipenem; and (ii) to define in vivo susceptibility breakpoints. METHODS: Mice were infected with a susceptible E. coli CFT073-RR or its transconjugant (CFT073-RR Tc) harbouring a blaCTX-M-15-carrying plasmid, using an ascending UTI model. Therapeutic regimens were chosen in order to reproduce percentage of time of free drug concentrations above MIC (fT>MIC) obtained in humans with standard regimens of temocillin (200 mg/kg every 2 h for 2 g every 12 h) or imipenem (100 mg/kg every 2 h for 1 g every 8 h). Additional regimens of temocillin (200 mg/kg every 4 and 6 h) with reduced fT>MIC were studied. RESULTS: MICs of temocillin and imipenem were 4/8 and 0.5/0.5 mg/L, for CFT073-RR and CFT073-RR Tc, respectively. In vivo, when given every 2 h (fT>MIC = 82% and 70%), temocillin was bactericidal and as effective as imipenem in kidneys against both strains without selecting resistant mutants. Temocillin remained active even when given every 4 h, generating an fT>MIC of 41% and 35%, which corresponded to a breakpoint of 16 mg/L in humans with the standard regimen. CONCLUSIONS: Our observations support the consideration of a standard regimen of temocillin as an alternative to carbapenems for the treatment of UTI due to CTX-M-producing E. coli strains with an MIC of 16 mg/L or less.

Quinolone-resistant Escherichia coli from the faecal microbiota of healthy volunteers after ciprofloxacin exposure are highly adapted to a commensal lifestyle.

OBJECTIVES: Quinolone-resistant Escherichia coli (QREC) primarily emerge in commensal bacteria under selective pressure. The aim of this work was to investigate the characteristics of QREC from the faecal microbiota after quinolone exposure, as they remain largely unknown. METHODS: Forty-eight healthy volunteers received ciprofloxacin from day 1 to day 14. QREC were detected in stools from 14 subjects at day 42. QREC were compared in terms of genetic background, metabolic properties, stress resistance and intestinal colonization abilities with quinolone-susceptible E. coli (QSEC) from the same 14 individuals and from 29 volunteers who remained QREC-free. RESULTS: QREC always belonged to a single clone for a given volunteer and to restricted phylogenetic groups. QREC carried significantly more iron capture systems than QSEC. Maximum growth rates in minimal medium with gluconate, general stress regulator RpoS activity assessed by iodine staining and resistance to oxidative and acid stresses were significantly higher for QREC than for QSEC. In a mouse colonization model, QREC efficiently colonized the intestine microbiota despite the presence of QSEC competitors. At day 42, QREC and QSEC faecal counts from the 14 volunteers were comparable except in three subjects where only QREC could be detected. CONCLUSIONS: These results suggest that QREC do not have a fitness cost, probably as a result of genetic co-selection, but are highly adapted to a commensal lifestyle. They may not be eliminated easily from the faecal microbiota from healthy subjects once selected.

Ciprofloxacin treatment failure in a murine model of pyelonephritis due to an AAC(6')-Ib-cr-producing Escherichia coli strain susceptible to ciprofloxacin in vitro.

AAC(6')-Ib-cr is a plasmid-mediated quinolone resistance mechanism described worldwide for Escherichia coli. Since it confers in vitro only a low level of resistance to ciprofloxacin, we evaluated its impact on the in vivo activity of ciprofloxacin. Isogenic strains were obtained by transferring plasmid p449, harboring aac(6')-Ib-cr, into the quinolone-susceptible strain E. coli CFT073-RR and its D87G gyrA mutant. MICs were 0.015, 0.06, 0.25, and 0.5 µg/ml against E. coli strains CFT073-RR, CFT073-RR/p449, CFT073-RR GyrA(r), and CFT073-RR GyrA(r)/p449, respectively. Bactericidal activity was reduced at 1× the MIC for the three resistant derivatives, while at a fixed concentration of 0.5 µg/ml, 99.9% killing was observed for all strains except E. coli CFT073-RR GyrA(r)/p449. In the murine model of pyelonephritis, an optimal regimen of ciprofloxacin (10 mg/kg of body weight twice a day [b.i.d.]) significantly decreased the bacterial count in the kidneys of mice infected with E. coli CFT073 (1.6 versus 4.3 log10 CFU/g of kidney compared to untreated controls; P = 0.0001), while no significant decrease was observed for E. coli CFT073-RR/p449 (2.7 versus 3.1 log10 CFU/g; P = 0.84), E. coli CFT073-RR GyrA(r) (4.2 versus 4.1 log10 CFU/g; P = 0.35), or E. coli CFT073-RR GyrA(r)/p449 (2.9 versus 3.6 log10 CFU/g; P = 0.47). While pharmacokinetic and pharmacodynamic (PK/PD) parameters accounted for ciprofloxacin failure against gyrA-containing mutants, this was not the case for the aac(6')-Ib-cr-containing strains, suggesting an in situ hydrolysis of ciprofloxacin in the latter case.

Rapid response of retinal pigment epithelial detachments to intravitreal aflibercept in neovascular age-related macular degeneration refractory to bevacizumab and ranibizumab.

PURPOSE: The aim of this study is to report the short-term efficacy of aflibercept in the treatment of neovascular age-related macular degeneration (AMD) with associated retinal pigment epithelial detachment (PED) which is refractory or develops tachyphylaxis to bevacizumab and ranibizumab. METHODS: The method comprised a retrospective review of the medical records of patients with neovascular AMD and associated PEDs recently treated with aflibercept and previously treated with bevacizumab and ranibizumab. RESULTS: Three eyes of three female patients of ages 49, 55, and 65 years old with large serous PEDs and subretinal fluid (SRF) associated with occult choroidal neovascularization and neovascular AMD were treated with aflibercept after intravitreal bevacizumab and/or ranibizumab failed to resolve the lesions. All had complete resolution of SRF and complete or near-complete resolution of the PEDs after aflibercept injections over a 3-month period. Visual acuity improved in all three eyes. CONCLUSION: Intravitreal aflibercept may be an effective treatment option for serous PED in neovascular AMD patients after bevacizumab and ranibizumab have previously failed. Larger studies with longer follow-up are required to determine the role of aflibercept in treatment of PED in neovascular AMD.

Clinical predictive values of extended-spectrum beta-lactamase carriage in patients admitted to medical wards.

We aimed to reassess, through clinical items, populations at risk for extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) carriage at admission to hospital and to assess the risk of further positive clinical culture of ESBL-E among carriers. We performed a 5-month cohort study in a medicine ward of a 500-bed university teaching hospital in the Parisian area of France. All admitted patients were prospectively enrolled for rectal swabbing and clinical data collection, including bacterial infection at admission and during stay. Variables associated with ESBL-E carriage were identified by univariate and multivariate analysis. Five hundred patients were included. The prevalence of ESBL-E was 6.6% (33/500) upon admission. Only previous carriage of multidrug-resistant bacteria (MDRB) was associated with carriage (odds ratio [OR]: 17.7, 95% confidence interval (CI) 5.8-54.2, p < 0.001), yet, the positive predictive value (PPV) was not higher than 50%. When prior MDRB carriage was not considered in the multivariate analysis, only prior antibiotic consumption was found to be associated with carriage at admission (OR: 2.2 [1.1-4.5], p = 0.02). Two patients had ESBL-E infection at admission, yet, no patient became infected with ESBL-E during their stay. The clinical prediction of ESBL carriage at admission in our wards was found to be poorly efficient for assessing the at-risk population.

Study of 2-H-heptafluoropropane and its thermal decomposition using UV photoelectron spectroscopy and ab initio molecular orbital calculations.

The thermal decomposition of 2-H-heptafluoropropane, CF(3)CHFCF(3), at low pressure, heavily diluted in argon, has been studied over the temperature range 600-2000 degrees C using photoelectron spectroscopy. Comparison of the results obtained has been made with results of recent electronic structure calculations of possible decomposition pathways and results of a shock tube study. The most favored reaction thermodynamically, to produce CF(3)CF=CF(2) + HF, is found to be the main decomposition reaction at lower temperatures, 600-900 degrees C. At higher temperatures, 900-1200 degrees C, the decomposition reaction to give C(2)F(4) + CF(3)H was found to become important. No evidence for CF(3)CHFCF(3) --> CF(3)CHF + CF(3), a reaction expected to be important from a shock tube study, performed at much higher pressures, or for CF(3)CHFCF(3) --> CF(3)CF + CF(3)H was obtained, although for the latter reaction it is likely that CF(3)CF converts into C(2)F(4) under the conditions used before photoionization, in the ionization region of the photoelectron spectrometer. At higher temperatures C(3)F(6) decomposes to C(2)F(4) + CF(2), and C(2)F(4) decomposes to CF(2). Ab initio calculations have been performed of the adiabatic and vertical ionization energies of possible primary pyrolysis products to assist assignment of the photoelectron spectra recorded for heated flowing gas samples. A comparison is made between the threshold photoelectron spectrum and the photoelectron spectrum of CF(3)CF=CF(2).

Study of pentafluoroethane and its thermal decomposition using UV photoelectron spectroscopy and ab initio molecular orbital calculations.

The UV photoelectron spectrum of CF(3)CHF(2) has been recorded and assigned using EOM-CCSD calculations. For the first band, the adiabatic ionization energy (AIE) and vertical ionization energy (VIE) have been measured as (12.71 +/- 0.05) and (13.76 +/- 0.02) eV, respectively. The measured AIE is higher than the recommended value from state-of-the-art ab initio calculations of (12.26 +/- 0.02) eV because of a large geometry change on ionization, mainly arising from a significant increase in the C-C bond length, which results in poor Franck-Condon factors in the adiabatic region. The experimental VIE also shows poor agreement with the computed value of 14.05 +/- 0.06 eV because, in the higher energy region of the first photoelectron band, dissociation of CF(3)CHF(2)(+) to CHF(2)(+) + CF(3) occurs. This has a calculated thermodynamic onset of (12.89 +/- 0.20) eV. Recommendations are made for the heats of formation, DeltaH(f,298)(slashed circle), of CF(3)CHF(2) and CF(3)CHF(2)(+), based on the results of the ab initio calculations. Pyrolysis of flowing CF(3)CHF(2) diluted in argon shows evidence of production of C(2)F(4) and HF at lower temperatures and CF(2) and CF(3)H at higher temperatures. The relative temperature dependence of the observed photoelectron bands associated with these molecules is interpreted in terms of two decomposition reactions of CF(3)CHF(2) as well as the reaction C(2)F(4) --> 2CF(2).

Catechol derivatives-coated Fe3O4 and gamma-Fe2O3 nanoparticles as potential MRI contrast agents.

Superparamagnetic iron oxide nanoparticles, Fe(3)O(4) and gamma-Fe(2)O(3), were produced by the so-called polyol process. In order to stabilize the particles in a physiological environment as potential contrast agents for Magnetic Resonance Imaging (MRI), the as-prepared particles were successfully transferred to an aqueous medium through ligand exchange chemistry of the adsorbed polyol species with the dopamine or the catechaldehyde. The ligands were able to participate in bidentate binding to the nanoparticles surface and to improve the stability of aqueous suspensions of the nanoparticles. Analysis was performed by various techniques including X-ray diffraction, transmission electron microscopy, infrared spectroscopy and thermal analysis. The results of magnetic measurements and initial in vitro magnetic resonance imaging essays are presented for the pre- and post-surface modified nanoparticles, respectively and discussed in relation with their structure and microstructure.

A liquid-filled tunable double-focus microlens.

A novel microlens design with tunable double-focus is presented. It is fabricated by adding only one SU-8 photolithography step to the well-developed liquid-filled microlens fabrication process. The thickness of this layer determines the thickness difference between the central and peripheral region of the membrane, the deformation of which is used to define the surface profile of the microlens. The stepped thickness variation is finally manifested as the difference in deformation contour at two different regions of the membrane when subjected to uniform applied pressure, thereby causing two focal lengths to appear. Experimental and simulation results are presented, from which the tunability of the focal lengths of the double-focus microlens is demonstrated to be effective over a wide range through combining the structural design with pressure control. The successful demonstration of this unconventional microlens design concept will potentially extend t application of liquid-filled microlens technology.