420 research outputs found
The very faint hard state of the persistent neutron star X-ray binary SLX 1737-282 near the Galactic centre
We report on a detailed study of the spectral and temporal properties of the
neutron star low mass X-ray binary SLX 1737-282, which is located only ~1degr
away from Sgr A. The system is expected to have a short orbital period, even
within the ultra-compact regime, given its persistent nature at low X-ray
luminosities and the long duration thermonuclear burst that it has displayed.
We have analysed a Suzaku (18 ks) observation and an XMM-Newton (39 ks)
observation taken 7 years apart. We infer (0.5-10 keV) X-ray luminosities in
the range 3-6 x10^35erg s-1, in agreement with previous findings. The spectra
are well described by a relatively cool (kTbb = 0.5 keV) black body component
plus a Comptonized emission component with {\Gamma} ~1.5-1.7. These values are
consistent with the source being in a faint hard state, as confirmed by the ~
20 per cent fractional root mean square amplitude of the fast variability (0.1
- 7 Hz) inferred from the XMM-Newton data. The electron temperature of the
corona is >7 keV for the Suzaku observation, but it is measured to be as low as
~2 keV in the XMM-Newton data at higher flux. The latter is significantly lower
than expected for systems in the hard state. We searched for X-ray pulsations
and imposed an upper limit to their semi-amplitude of 2 per cent (0.001 - 7
Hz). Finally, we investigated the origin of the low frequency variability
emission present in the XMM-Newton data and ruled out an absorption dip origin.
This constraint the orbital inclination of the system to 65 degr unless the
orbital period is longer than 11 hr (i.e. the length of the XMM-Newton
observation).Comment: 7 pages, 4 figures, 1 table. Accepted for publication in MNRA
The optical counterpart of the bright X-ray transient Swift J1745-26
We present a 30-day monitoring campaign of the optical counterpart of the
bright X-ray transient Swift J1745-26, starting only 19 minutes after the
discovery of the source. We observe the system peaking at i' ~17.6 on day 6
(MJD 56192) to then decay at a rate of ~0.04 mag/day. We show that the optical
peak occurs at least 3 days later than the hard X-ray (15-50 keV) flux peak.
Our measurements result in an outburst amplitude greater than 4.3 magnitudes,
which favours an orbital period < 21 h and a companion star with a spectral
type later than ~ A0. Spectroscopic observations taken with the GTC-10.4 m
telescope reveal a broad (FWHM ~ 1100 km/s), double-peaked H_alpha emission
line from which we constrain the radial velocity semi-amplitude of the donor to
be K_2 > 250 km/s. The breadth of the line and the observed optical and X-ray
fluxes suggest that Swift J1745-26 is a new black hole candidate located closer
than ~7 kpc.Comment: 5 pages, 4 figures, accepted for publication in MNRA
Importance of tissue sampling, laboratory methods, and patient characteristics for detection of Pneumocystis in autopsied lungs of non-immunosuppressed individuals
To understand the epidemiological significance of Pneumocystis detection in a lung tissue sample of non-immunosuppressed individuals, we examined sampling procedures, laboratory methodology, and patient characteristics of autopsy series reported in the literature. Number of tissue specimens, DNA-extraction procedures, age and underlying diagnosis highly influence yield and are critical to understand yield differences of Pneumocystis among reports of pulmonary colonization in immunocompetent individuals.publishersversionpublishe
Proposing environmental flows based on physical habitat simulation for five fish species in the Lower Duero River Basin, Mexico
The concept of “environmental flow” is defined as hydrologic regimes that are required to sustain ecosystem health and functions in rivers. In Mexico, it has become an important topic, not least because a 2012 legal standard (NMX-AA-159-SCFI-2012), establishes procedures for determining instream flow requirements. Goals. The aim of this paper is to propose an acceptable environmental flow requirement for a regulated river segment in the Duero River Basin in, Michoacan, Mexico. Methods. Of the many methods of establishing environmental flows in rivers, this article is concerned with the habitat simulation method. This is based on the IFIM theoretical framework and the PHABSIM mathematical model, by which the WUA-Q curves were obtained for five species of fish. Results. From these curves, we determined that the Goodea atripinnis species has the greater habitat area and reached a maximum of 4338 m2/km for a flow of 5 m3/s; Alloophorus robustus maintained a constant habitat of 2000 m2/km between flow rates of 5 to 15 m3/s. With smaller area, Menidia jordani had a maximum habitat of 1323 m2/km for 4.5 m3/s; and with WUA less than 500 m2/km the curves of the species Algansea tincella and Aztecula sallaei were obtained. Conclusions. The average regulation in March and April was 3.61 and 3.44 m3/s and with the EFR proposal it was 5.11 and 5.00 m3/s for March and April, respectively. In general, the monthly environmental regime is to maintain 80% of the natural flow regime, generating an increase in habitat during the dry season of 24% for A. robustus and 23% for A. sallaei
Discovery of potent and selective inhibitors of the Escherichia coli M1-aminopeptidase via multicomponent solid-phase synthesis of tetrazole-peptidomimetics
The Escherichia coli neutral M1-aminopeptidase (ePepN) is a novel target identified for the development of antimicrobials. Here we describe a solid-phase multicomponent approach which enabled the discovery of potent ePepN inhibitors. The on-resin protocol, developed in the frame of the Distributed Drug Discovery (D3) program, comprises the implementation of parallel Ugi-azide four-component reactions with resin-bound amino acids, thus leading to the rapid preparation of a focused library of tetrazole-peptidomimetics (TPMs) suitable for biological screening. By dose-response studies, three compounds were identified as potent and selective ePepN inhibitors, as little inhibitory effect was exhibited for the porcine ortholog aminopeptidase. The study allowed for the identification of the key structural features required for a high ePepN inhibitory activity. The most potent and selective inhibitor (TPM 11) showed a non-competitive inhibition profile of ePepN. We predicted that both diastereomers of compound TPM 11 bind to a site distinct from that occupied by the substrate. Theoretical models suggested that TPM 11 has an alternative inhibition mechanism that doesn't involve Zn coordination. On the other hand, the activity landscape analysis provided a rationale for our findings. Of note, compound TMP 2 showed in vitro antibacterial activity against Escherichia coli. Furthermore, none of the three identified inhibitors is a potent haemolytic agent, and only two compounds showed moderate cytotoxic activity toward the murine myeloma P3X63Ag cells. These results point to promising compounds for the future development of rationally designed TPMs as antibacterial agents
Roles of non-coding RNA in sugarcane-microbe interaction
Studies have highlighted the importance of non-coding RNA regulation in plant-microbe
interaction. However, the roles of sugarcane microRNAs (miRNAs) in the regulation of disease
responses have not been investigated. Firstly, we screened the sRNA transcriptome of sugarcane
infected with Acidovorax avenae. Conserved and novel miRNAs were identified. Additionally,
small interfering RNAs (siRNAs) were aligned to differentially expressed sequences from the
sugarcane transcriptome. Interestingly, many siRNAs aligned to a transcript encoding a coppertransporter
gene whose expression was induced in the presence of A. avenae, while the siRNAs were
repressed in the presence of A. avenae. Moreover, a long intergenic non-coding RNA was identified
as a potential target or decoy of miR408. To extend the bioinformatics analysis, we carried out
independent inoculations and the expression patterns of six miRNAs were validated by quantitative
reverse transcription-PCR (qRT-PCR). Among these miRNAs, miR408—a copper- microRNA—was
downregulated. The cleavage of a putative miR408 target, a laccase, was confirmed by a modified
50RACE (rapid amplification of cDNA ends) assay. MiR408 was also downregulated in samples
infected with other pathogens, but it was upregulated in the presence of a beneficial diazotrophic
bacteria. Our results suggest that regulation by miR408 is important in sugarcane sensing whether
microorganisms are either pathogenic or beneficial, triggering specific miRNA-mediated regulatory
mechanisms accordingly
Geologic carbon sources may confound ecosystem carbon balance estimates: Evidence from a semiarid steppe in the southeast of Spain
At a semiarid steppe site located in the SE of Spain, relatively large CO2 emissions were measured that could not be attributed to the ecosystem activity alone. Since the study site was located in a tectonically active area, it was hypothesized that a part of the measured CO2 was of geologic origin. This investigation included a survey of soil CO2 efflux, together with carbon isotope analyses of the CO2 in the soil atmosphere, soil CO2 efflux (ie, Keeling plots), groundwater and local thermal springs. These measurements confirmed the ... Articoli in Schola
- …