On the origin of the correlations between the accretion luminosity and emission line luminosities in pre-main-sequence stars

Correlations between the accretion luminosity and emission line luminosities (Lacc and Lline) of pre-main-sequence (PMS) stars have been published for many different spectral lines, which are used to estimate accretion rates. Despite the origin of those correlations is unknown, this could be attributed to direct or indirect physical relations between the emission line formation and the accretion mechanism. This work shows that all (near-UV/optical/near-IR) Lacc-Lline correlations are the result of the fact that the accretion luminosity and the stellar luminosity (L*) are correlated, and are not necessarily related with the physical origin of the line. Synthetic and observational data are used to illustrate how the Lacc-Lline correlations depend on the Lacc-L* relationship. We conclude that because PMS stars show the Lacc-L* correlation immediately implies that Lacc also correlates with the luminosity of all emission lines, for which the Lacc-Lline correlations alone do not prove any physical connection with accretion but can only be used with practical purposes to roughly estimate accretion rates. When looking for correlations with possible physical meaning, we suggest that Lacc/L* and Lline/L* should be used instead of Lacc and Lline. Finally, the finding that Lacc has a steeper dependence on L* for T Tauri stars than for intermediate-mass Herbig Ae/Be stars is also discussed. That is explained from the magnetospheric accretion scenario and the different photospheric properties in the near-U

Chemotherapy versus supportive care in advanced non-small cell lung cancer: improved survival without detriment to quality of life

BACKGROUND: In 1995 a meta-analysis of randomised trials investigating the value of adding chemotherapy to primary treatment for non-small cell lung cancer (NSCLC) suggested a small survival benefit for cisplatin-based chemotherapy in each of the primary treatment settings. However, the metaanalysis included many small trials and trials with differing eligibility criteria and chemotherapy regimens. METHODS: The aim of the Big Lung Trial was to confirm the survival benefits seen in the meta-analysis and to assess quality of life and cost in the supportive care setting. A total of 725 patients were randomised to receive supportive care alone (n = 361) or supportive care plus cisplatin-based chemotherapy (n = 364). RESULTS: 65% of patients allocated chemotherapy (C) received all three cycles of treatment and a further 27% received one or two cycles. 74% of patients allocated no chemotherapy (NoC) received thoracic radiotherapy compared with 47% of the C group. Patients allocated C had a significantly better survival than those allocated NoC: HR 0.77 (95% CI 0.66 to 0.89, p = 0.0006), median survival 8.0 months for the C group v 5.7 months for the NoC group, a difference of 9 weeks. There were 19 (5%) treatment related deaths in the C group. There was no evidence that any subgroup benefited more or less fromchemotherapy. No significant differences were observed between the two groups in terms of the pre-defined primary and secondary quality of life end points, although large negative effects of chemotherapy were ruled out. The regimens used proved to be cost effective, the extra cost of chemotherapy being offset by longer survival. CONCLUSIONS: The survival benefit seen in this trial was entirely consistent with the NSCLC meta-analysis and subsequent similarly designed large trials. The information on quality of life and cost should enablepatients and their clinicians to make more informed treatment choices

High-resolution Br γ spectro-interferometry of the transitional Herbig Ae/Be star HD 100546: a Keplerian gaseous disc inside the inner rim

We present spatially and spectrally resolved Br γ emission around the planet-hosting, transitional Herbig Ae/Be star HD 100546. Aiming to gain insight into the physical origin of the line in possible relation to accretion processes, we carried out Br γ spectro-interferometry using AMBER/VLTI from three different baselines achieving spatial and spectral resolutions of 2–4 mas and 12 000. The Br γ visibility is larger than that of the continuum for all baselines. Differential phases reveal a shift between the photocentre of the Br γ line – displaced ∼0.6 mas (0.06 au at 100 pc) NE from the star – and that of the K-band continuum emission – displaced ∼0.3 mas NE from the star. The photocentres of the redshifted and blueshifted components of the Br γ line are located NW and SE from the photocentre of the peak line emission, respectively. Moreover, the photocentre of the fastest velocity bins within the spectral line tends to be closer to that of the peak emission than the photocentre of the slowest velocity bins. Our results are consistent with a Br γ-emitting region inside the dust inner rim ( ≲ 0.25 au) and extending very close to the central star, with a Keplerian, disc-like structure rotating counter-clockwise, and most probably flared (∼25°). Even though the main contribution to the Br γ line does not come from gas magnetically channelled on to the star, accretion on to HD 100546 could be magnetospheric, implying a mass accretion rate of a few 10−7 M⊙ yr−1. This value indicates that the observed gas has to be replenished on time-scales of a few months to years, perhaps by planet-induced flows from the outer to the inner disc as has been reported for similar systems

On the origin of the correlations between the accretion luminosity and emission line luminosities in pre-main-sequence stars

Correlations between the accretion luminosity and emission line luminosities (Lacc and Lline) of pre-main-sequence (PMS) stars have been published for many different spectral lines, which are used to estimate accretion rates. Despite the origin of those correlations is unknown, this could be attributed to direct or indirect physical relations between the emission line formation and the accretion mechanism. This work shows that all (near-UV/optical/near-IR) Lacc–Lline correlations are the result of the fact that the accretion luminosity and the stellar luminosity (L*) are correlated, and are not necessarily related with the physical origin of the line. Synthetic and observational data are used to illustrate how the Lacc–Lline correlations depend on the Lacc–L* relationship. We conclude that because PMS stars show the Lacc–L* correlation immediately implies that Lacc also correlates with the luminosity of all emission lines, for which the Lacc–Lline correlations alone do not prove any physical connection with accretion but can only be used with practical purposes to roughly estimate accretion rates. When looking for correlations with possible physical meaning, we suggest that Lacc/L* and Lline/L* should be used instead of Lacc and Lline. Finally, the finding that Lacc has a steeper dependence on L* for T Tauri stars than for intermediate-mass Herbig Ae/Be stars is also discussed. That is explained from the magnetospheric accretion scenario and the different photospheric properties in the near-UV

The antimicrobial activity of a carbon monoxide releasing molecule (EBOR-CORM-1) is shaped by intraspecific variation within3 Pseudomonas aeruginosa populations

Carbon monoxide releasing molecules (CORMs) have been suggested as a new synthetic class of antimicrobials to treat bacterial infections. Here we utilized a novel EBOR-CORM-1 ([NEt4][MnBr2(CO)4]) capable of water-triggered CO-release, and tested its efficacy against a collection of clinical Pseudomonas aeruginosa strains that differ in infection-related virulence traits. We found that while EBOR-CORM-1 was effective in clearing planktonic and biofilm cells of P. aeruginosa strain PAO1 in a concentration dependent manner, this effect was less clear and varied considerably between different P. aeruginosa cystic fibrosis (CF) lung isolates. While a reduction in cell growth was observed after 8 h of CORM application, either no effect or even a slight increase in cell densities and the amount of biofilm was observed after 24 h. This variation could be partly explained by differences in bacterial virulence traits: while CF isolates showed attenuated in vivo virulence and growth compared to strain PAO1, they formed much more biofilm, which could have potentially protected them from the CORM. Even though no clear therapeutic benefits against a subset of isolates was observed in an in vivo wax moth acute infection model, EBOR-CORM-1 was more efficient at reducing the growth of CF isolate co-culture populations harboring intraspecific variation, in comparison with efficacy against more uniform single isolate culture populations. Together these results suggest that CORMs could be effective at controlling genetically diverse P. aeruginosa populations typical for natural chronic CF infections and that the potential benefits of some antibiotics might not be observed if tested only against clonal bacterial populations

Reactivity of a Dinuclear PdIComplex [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] with PPh3 : Implications for Cross-Coupling Catalysis Using the Ubiquitous Pd(OAc)2/nPPh3Catalyst System

[PdI2(μ-PPh2)(μ2-OAc)(PPh3)2] is the reduction product of PdII(OAc)2(PPh3)2, generated by reaction of ‘Pd(OAc)2’ with two equivalents of PPh3. Here, we report that the reaction of [PdI2(μ-PPh2)(μ2-OAc)(PPh3)2] with PPh3results in a nuanced disproportionation reaction, forming [Pd0(PPh3)3] and a phosphinito-bridged PdI-dinuclear complex, namely [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2]. The latter complex is proposed to form by abstraction of an oxygen atom from an acetate ligand at Pd. A mechanism for the formal reduction of a putative PdIIdisproportionation species to the observed PdIcomplex is postulated. Upon reaction of the mixture of [Pd0(PPh)3] and [PdI2(μ-PPh2){κ2-P,O-μ-P(O)Ph2}(κ-PPh3)2] with 2-bromopyridine, the former Pd0complex undergoes a fast oxidative addition reaction, while the latter dinuclear PdIcomplex converts slowly to a tripalladium cluster, of the type [Pd3(μ-X)(μ-PPh2)2(PPh3)3]X, with an overall 4/3 oxidation stateperPd. Our findings reveal complexity associated with the precatalyst activation step for the ubiquitous ‘Pd(OAc)2’/nPPh3catalyst system, with implications for cross-coupling catalysis

Norspermidine is not a self-produced trigger for biofilm disassembly

SummaryFormation of Bacillus subtilis biofilms, consisting of cells encapsulated within an extracellular matrix of exopolysaccharide and protein, requires the polyamine spermidine. A recent study reported that (1) related polyamine norspermidine is synthesized by B. subtilis using the equivalent of the Vibrio cholerae biosynthetic pathway, (2) exogenous norspermidine at 25 μM prevents B. subtilis biofilm formation, (3) endogenous norspermidine is present in biofilms at 50–80 μM, and (4) norspermidine prevents biofilm formation by condensing biofilm exopolysaccharide. In contrast, we find that, at concentrations up to 200 μM, exogenous norspermidine promotes biofilm formation. We find that norspermidine is absent in wild-type B. subtilis biofilms at all stages, and higher concentrations of exogenous norspermidine eventually inhibit planktonic growth and biofilm formation in an exopolysaccharide-independent manner. Moreover, orthologs of the V. cholerae norspermidine biosynthetic pathway are absent from B. subtilis, confirming that norspermidine is not physiologically relevant to biofilm function in this species