761 research outputs found
The redox-active drug metronidazole and thiol-depleting garlic compounds act synergistically in the protist parasite Spironucleus vortens
Spironucleus vortens is a protozoan parasite associated with significant mortalities in the freshwater angelfish, Pterophyllum scalare. Control of this parasite is especially problematic due to restrictions on the use of the drug of choice, metronidazole (MTZ), on fish farms. Use of garlic (Allium sativum) is undergoing a renaissance following experimental validations of its antimicrobial efficiency. Ajoene ((E,Z)-4,5,9-trithiadodeca-1,6,11-triene 9-oxide), is a stable transformation product of allicin, the primary biologically active component of garlic. In the current study, an ajoene oil crude extract had a minimum inhibitory concentration (MIC) of 40 μg/ml against S. vortens. GC-MS and NMR spectroscopy revealed this ajoene extract contained a mixture of the (E) and (Z)-ajoene isomers along with diallyl disulphide (DADS) and diallyl trisulphide (DATS). The only component of the ajoene crude oil found to substantially inhibit S. vortens growth by optical density monitoring (Bioscreen C Reader) was (Z)-ajoene (MIC 16 μg/ml). Ajoene oil acted in synergy with MTZ in vitro, reducing the individual MIC of this drug (4 μg/ml) by 16-fold, and that of ajoene oil by 200-fold with a fractional inhibitory concentration (FIC) index of 0.263. This synergistic interaction was confirmed in vivo. S. vortens-infected P. scalare angelfish dosed orally with 0.5% (v/w) MTZ combined with 0.05% (v/w) ajoene displayed a significant reduction in faecal trophozoite count, whilst those fed on 0.5% MTZ flakes (half the recommended oral dose) alone did not. This study demonstrates for the first time the synergistic interaction between the synthetic drug MTZ and natural ajoene oil both in vitro and in vivo. Future work should evaluate the potential synergy of ajoene and MTZ against MTZ-resistant bacteria and protists
Deciphering the Activity and Quiescence of High-redshift Cluster Environments : ALMA Observations of Cl J1449+0856 at z=2
We present Atacama Large Millimeter/submillimeter Array observations of the 870 mu m continuum and CO(4-3) line emission in the core of the galaxy cluster Cl J1449+0856 at z = 2, a near-IR-selected, X-ray-detected system in the mass range of typical progenitors of today's massive clusters. The 870 mu m map reveals six F-870 mu m > 0.5 mJy sources spread over an area of 0.07 arcmin(2), giving an overdensity of a factor of similar to 10 (6) with respect to blank-field counts down to F-870 mu m > 1 mJy (> 0.5 mJy). On the other hand, deep CO(4-3) follow-up confirms membership of three of these sources but suggests that the remaining three, including the brightest 870 mu m sources in the field (F-870 mu m greater than or similar to 2 mJy), are likely interlopers. The measurement of 870 mu m continuum and CO(4-3) line fluxes at the positions of previously known cluster members provides a deep probe of dusty star formation occurring in the core of this high-redshift structure, adding up to a total star formation rate of similar to 700 +/- 100 M-circle dot yr(-1) and yielding an integrated star formation rate density of similar to 10(4) M-circle dot yr(-1) Mpc(-3), five orders of magnitude larger than in the field at the same epoch, due to the concentration of star-forming galaxies in the small volume of the dense cluster core. The combination of these observations with previously available Hubble Space Telescope imaging highlights the presence in this same volume of a population of galaxies with already suppressed star formation. This diverse composition of galaxy populations in Cl J1449+0856 is especially highlighted at the very cluster center, where a complex assembly of quiescent and star-forming sources is likely forming the future brightest cluster galaxy.Peer reviewe
Merger driven star-formation activity in Cl J1449+0856 at z=1.99 as seen by ALMA and JVLA
We use ALMA and JVLA observations of the galaxy cluster Cl J1449+0856 at z=1.99, in order to study how dust-obscured star-formation, ISM content and AGN activity are linked to environment and galaxy interactions during the crucial phase of high-z cluster assembly. We present detections of multiple transitions of 12CO, as well as dust continuum emission detections from 11 galaxies in the core of Cl J1449+0856. We measure the gas excitation properties, star-formation rates, gas consumption timescales and gas-to-stellar mass ratios for the galaxies.
We find evidence for a large fraction of galaxies with highly-excited molecular gas, contributing >50% to the total SFR in the cluster core. We compare these results with expectations for field galaxies, and conclude that environmental influences have strongly enhanced the fraction of excited galaxies in this cluster. We find a dearth of molecular gas in the galaxies' gas reservoirs, implying a high star-formation efficiency (SFE) in the cluster core, and find short gas depletion timescales τ<0.1-0.4 Gyrs for all galaxies. Interestingly, we do not see evidence for increased specific star-formation rates (sSFRs) in the cluster galaxies, despite their high SFEs and gas excitations. We find evidence for a large number of mergers in the cluster core, contributing a large fraction of the core's total star-formation compared with expectations in the field. We conclude that the environmental impact on the galaxy excitations is linked to the high rate of galaxy mergers, interactions and active galactic nuclei in the cluster core
The [C II] emission as a molecular gas mass tracer in galaxies at low and high redshift
We present ALMA Band 9 observations of the [C II]158um emission for a sample of 10 main-sequence galaxies at redshift z ~ 2, with typical stellar masses (log M*/Msun ~ 10.0 - 10.9) and star formation rates (~ 35 - 115 Msun/yr). Given the strong and well understood evolution of the interstellar medium from the present to z = 2, we investigate the behaviour of the [C II] emission and empirically identify its primary driver. We detect [C II] from six galaxies (four secure, two tentative) and estimate ensemble averages including non detections. The [C II]-to-infrared luminosity ratio (L[C II]/LIR) of our sample is similar to that of local main-sequence galaxies (~ 2 x 10^-3), and ~ 10 times higher than that of starbursts. The [C II] emission has an average spatial extent of 4 - 7 kpc, consistent with the optical size. Complementing our sample with literature data, we find that the [C II] luminosity correlates with galaxies' molecular gas mass, with a mean absolute deviation of 0.2 dex and without evident systematics: the [C II]-to-H2 conversion factor (alpha_[C II] ~ 30 Msun/Lsun) is largely independent of galaxies' depletion time, metallicity, and redshift. [C II] seems therefore a convenient tracer to estimate galaxies' molecular gas content regardless of their starburst or main-sequence nature, and extending to metal-poor galaxies at low and high redshifts. The dearth of [C II] emission reported for z > 6 - 7 galaxies might suggest either a high star formation efficiency or a small fraction of UV light from star formation reprocessed by dust
Defining the origins of multiple emission/excitation in rhenium-bisthiazole complexes
The underlying mechanism of the unusual emissive behavior of [Re(CO) 3 -1,1-bis-4-thiazole-(1,4)-diaminobutane)] bromide (4-BT) has been investigated. Synthesis and spectroscopic characterization of structurally similar isomers ([Re(CO) 3 -1,1-bis-2-thiazole-(1,4)-diaminobutane)] bromide (2-BT)) and the location of triplet states, solid state and low temperature spectroscopic measurements, and DFT calculations show that the photophysical properties are not due to photoisomerization as previously hypothesized. The results show that the unusual emissive behavior is not observed in structural isomers, is specific to the previously reported complex, 4-BT, and may arise from vibrational energy relaxation and vibrational cooling. Translation of the unusual emissive behavior to the solid state offers an interesting platform allowing this complex to be potentially utilized as a probe, sensor or photonic device
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Advanced oxidation technologies for chemical demilitarization
This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. The main project objective was to establish a technical basis for future program development in the area of chemical warfare agent destruction using a Los Alamos-developed advanced oxidation process: a two-stage device consisting of thermal packed-bed reactor (PBR) and a nonthermal plasma (NTP) reactor. Various compounds were evaluated as potential surrogates for chemical warfare (CW) agents. Representative effluent mass balances were projected for future comparisons with incinerators. The design and construction of lab-scale PBR/NTP reactors (consisting of a liquid injection and metering system, electric furnace, condensers, chemical traps, plasma reactors, power supplies, and chemical diagnostics) has been completed. This equipment, the experience gained from chemical-processing experiments, process modeling, and an initial demonstration of the feasibility of closed-loop operation, have provided a technical basis for further demonstrations and program development efforts
Social Cost Guarantees in Smart Route Guidance
We model and study the problem of assigning traffic in an urban road network
infrastructure. In our model, each driver submits their intended destination
and is assigned a route to follow that minimizes the social cost (i.e., travel
distance of all the drivers). We assume drivers are strategic and try to
manipulate the system (i.e., misreport their intended destination and/or
deviate from the assigned route) if they can reduce their travel distance by
doing so. Such strategic behavior is highly undesirable as it can lead to an
overall suboptimal traffic assignment and cause congestion. To alleviate this
problem, we develop moneyless mechanisms that are resilient to manipulation by
the agents and offer provable approximation guarantees on the social cost
obtained by the solution. We then empirically test the mechanisms studied in
the paper, showing that they can be effectively used in practice in order to
compute manipulation resistant traffic allocations
Rotation Curves in z ∼ 1–2 Star-forming Disks: Evidence for Cored Dark Matter Distributions
We report high quality, Halpha or CO rotation curves (RCs) to several Re for
41 large, massive, star-forming disk galaxies (SFGs), across the peak of cosmic
galaxy evolution (z~0.67-2.45), taken with the ESO-VLT, the LBT and IRAM-NOEMA.
Most RC41 SFGs have reflection symmetric RCs plausibly described by equilibrium
dynamics. We fit the major axis position-velocity cuts with beam-convolved,
forward modeling with a bulge, a turbulent rotating disk, and a dark matter
(DM) halo. We include priors for stellar and molecular gas masses, optical
light effective radii and inclinations, and DM masses from abundance matching
scaling relations. Two-thirds or more of the z>1.2 SFGs are baryon dominated
within a few Re of typically 5.5 kpc, and have DM fractions less than maximal
disks (=0.12). At lower redshift (z<1.2) that fraction is less than
one-third. DM fractions correlate inversely with the baryonic angular momentum
parameter, baryonic surface density and bulge mass. Inferred low DM fractions
cannot apply to the entire disk & halo but more plausibly reflect a flattened,
or cored, inner DM density distribution. The typical central 'DM deficit' in
these cores relative to NFW distributions is ~30% of the bulge mass. The
observations are consistent with rapid radial transport of baryons in the first
generation massive gas rich halos forming globally gravitationally unstable
disks, and leading to efficient build-up of massive bulges and central black
holes. A combination of heating due to dynamical friction and AGN feedback may
drive DM out of the initial cusps.Comment: 15 figures, 4 tables, accepted for publication in Ap
Non-state space: The strategic ejection of dangerous and high maintenance urban space
Some commentators have characterised so-called ‘no-go’ areas as sites in which the
exercise of authority is prevented. Here we suggest that many such spaces are produced by
state, policing and citizen repertoires that aim to minimise the costs and risks of engaging,
supporting and servicing such spaces and their populations. In this article we locate
strategies of public spending, policing and political action that offer a governing logic in
which neighbourhoods are essentially subtracted from the constitution of the city. During
such designations the assurances of citizenship, vitality of civic institutions and presence of
policing may be partially or wholly suspended. We present a framework for the
identification of such strategies in which these forms of social, political and spatial exiting
are described as being autotomic in nature – spaces that are ejected in order to avoid losses
or further damage to the body politic of the city in ways akin to the response of certain
animals that protect themselves from predation by shedding a limb or body part. This term
adds force and depth to assessments of the ways in which both temporary and more
sustained exits by policing, management and state servicing are designed in order to avoid
responsibility over, or engagement with, spaces that are deemed a threat in order to
maintain the integrity of the remaining, included city
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