4,643 research outputs found
The unusual distribution of molecular gas and star formation in Arp 140
We investigate the atomic and molecular interstellar medium and star
formation of NGC 275, the late-type spiral galaxy in Arp 140, which is
interacting with NGC 274, an early-type system. The atomic gas (HI)
observations reveal a tidal tail from NGC 275 which extends many optical radii
beyond the interacting pair. The HI morphology implies a prograde encounter
between the galaxy pair approximately 1.5 x 10**8 years ago. The Halpha
emission from NGC 275 indicates clumpy irregular star-formation, clumpiness
which is mirrored by the underlying mass distribution as traced by the Ks-band
emission. The molecular gas distribution is striking in its anti-correlation
with the {HII regions. Despite the evolved nature of NGC 275's interaction and
its barred potential, neither the molecular gas nor the star formation are
centrally concentrated. We suggest that this structure results from stochastic
star formation leading to preferential consumption of the gas in certain
regions of the galaxy. In contrast to the often assumed picture of interacting
galaxies, NGC 275, which appears to be close to merger, does not display
enhanced or centrally concentrated star formation. If the eventual merger is to
lead to a significant burst of star formation it must be preceded by a
significant conversion of atomic to molecular gas as at the current rate of
star formation all the molecular gas will be exhausted by the time the merger
is complete.Comment: 13 paper, accepted my Monthly Notices of the Royal Astronomical
Societ
The efficacy of halofantrine in the treatment of acute malaria in nonimmune travelers
A multicenter prospective trial was performed to investigate the efficacy and the tolerability of halofantrine in nonimmune patients with malaria imported from areas with drug-resistant falciparum parasites (mainly Africa). Forty-five of the 74 subjects were treated with a one-day regimen (3 x 500 mg) of halofantrine, and the other 29 received the same regimen with an additional treatment on day 7. In the second group, a 100% efficacy rate was demonstrated, but in the group receiving the one-day regimen, four recrudescences were observed in patients with falciparum malaria. Only five mild adverse reactions were seen, which disappeared spontaneously after the end of the treatment. We conclude that halofantrine is highly effective in curing malaria in nonimmune subjects. The treatment scheme for such persons should include an additional treatment on day 7 for nonimmune individuals. This drug was well tolerated in our patients, indicating that halofantrine will be useful in the treatment of multidrug-resistant malaria in nonimmune persons
A SUBTLE INFRARED EXCESS ASSOCIATED WITH A YOUNG WHITE DWARF IN THE EDINBURGH-CAPE BLUE OBJECT SURVEY
We report the discovery of a subtle infrared excess associated with the young white dwarf EC 05365–4749 at 3.35 and 4.6 μ m. Follow-up spectroscopic observations are consistent with a hydrogen atmosphere white dwarf of effective temperature 22,800 K and log [ g (cm s{sup −2})] = 8.19. High-resolution spectroscopy reveals atmospheric metal pollution with logarithmic abundances of [Mg/H] = −5.36 and [Ca/H] = −5.75, confirming the white dwarf is actively accreting from a metal-rich source with an intriguing abundance pattern. We find that the infrared excess is well modeled by a flat, opaque debris disk, though disk parameters are not well constrained by the small number of infrared excess points. We further demonstrate that relaxing the assumption of a circular dusty debris disk to include elliptical disks expands the widths of acceptable disks, adding an alternative interpretation to the subtle infrared excesses commonly observed around young white dwarfs
On the completeness of impulsive gravitational wave space-times
We consider a class of impulsive gravitational wave space-times, which
generalize impulsive pp-waves. They are of the form ,
where is a Riemannian manifold of arbitrary dimension and carries
the line element with the line
element of and the Dirac measure. We prove a completeness result
for such space-times with complete Riemannian part .Comment: 13 pages, minor changes suggested by the referee
Fortnightly Fluctuations in the O-C Diagram of CS 1246
Dominated by a single, large-amplitude pulsation mode, the rapidly-pulsating
hot subdwarf B star CS 1246 is a prime candidate for a long-term O-C diagram
study. We collected nearly 400 hours of photometry with the PROMPT telescopes
over a time span of 14 months to begin looking for secular variations in the
pulse timings. Interestingly, the O-C diagram is dominated by a strong
sinusoidal pattern with a period of 14.1 days and an amplitude of 10.7
light-seconds. Underneath this sine wave is a secular trend implying a decrease
in the 371.7-s pulsational period of Pdot = -1.9 x 10^-11, which we attribute
to the evolution of the star through the H-R diagram. The sinusoidal variation
could be produced by the presence of a low-mass companion, with m sin i ~ 0.12
Msun, orbiting the subdwarf B star at a distance of 20 Rsun. An analysis of the
combined light curve reveals the presence of a low-amplitude first harmonic to
the main pulsation mode.Comment: Accepted for publication in MNRAS. 11 pages, 8 figures, 5 table
Validation of frequency and mode extraction calculations from time-domain simulations of accelerator cavities
The recently developed frequency extraction algorithm [G.R. Werner and J.R.
Cary, J. Comp. Phys. 227, 5200 (2008)] that enables a simple FDTD algorithm to
be transformed into an efficient eigenmode solver is applied to a realistic
accelerator cavity modeled with embedded boundaries and Richardson
extrapolation. Previously, the frequency extraction method was shown to be
capable of distinguishing M degenerate modes by running M different simulations
and to permit mode extraction with minimal post-processing effort that only
requires solving a small eigenvalue problem. Realistic calculations for an
accelerator cavity are presented in this work to establish the validity of the
method for realistic modeling scenarios and to illustrate the complexities of
the computational validation process. The method is found to be able to extract
the frequencies with error that is less than a part in 10^5. The corrected
experimental and computed values differ by about one parts in 10^$, which is
accounted for (in largest part) by machining errors. The extraction of
frequencies and modes from accelerator cavities provides engineers and
physicists an understanding of potential cavity performance as it depends on
shape without incurring manufacture and measurement costs
Characterisation of a highly potent and near pan-neutralising anti-HIV monoclonal antibody expressed in tobacco plants
Background
HIV remains one of the most important health issues worldwide, with almost 40 million people living with HIV. Although patients develop antibodies against the virus, its high mutation rate allows evasion of immune responses. Some patients, however, produce antibodies that are able to bind to, and neutralise different strains of HIV. One such ‘broadly neutralising’ antibody is ‘N6’. Identified in 2016, N6 can neutralise 98% of HIV-1 isolates with a median IC50 of 0.066 µg/mL. This neutralisation breadth makes N6 a very promising therapeutic candidate.
Results
N6 was expressed in a glycoengineered line of N. benthamiana plants (pN6) and compared to the mammalian cell-expressed equivalent (mN6). Expression at 49 mg/kg (fresh leaf tissue) was achieved in plants, although extraction and purification are more challenging than for most plant-expressed antibodies. N-glycoanalysis demonstrated the absence of xylosylation and a reduction in α(1,3)-fucosylation that are typically found in plant glycoproteins. The N6 light chain contains a potential N-glycosylation site, which was modified and displayed more α(1,3)-fucose than the heavy chain. The binding kinetics of pN6 and mN6, measured by surface plasmon resonance, were similar for HIV gp120. pN6 had a tenfold higher affinity for FcγRIIIa, which was reflected in an antibody-dependent cellular cytotoxicity assay, where pN6 induced a more potent response from effector cells than that of mN6. pN6 demonstrated the same potency and breadth of neutralisation as mN6, against a panel of HIV strains.
Conclusions
The successful expression of N6 in tobacco supports the prospect of developing a low-cost, low-tech production platform for a monoclonal antibody cocktail to control HIV in low-to middle income countries
Invasiveness of previous treatment for peripheral arterial disease and risk of adverse cardiac events after coronary stenting
Patients with peripheral arterial disease (PADs), undergoing percutaneous coronary intervention (PCI), have higher adverse event risks. The effect of invasiveness of PADs treatment on PCI outcome is unknown. This study assessed the impact of the invasiveness of previous PADs treatment (invasive or non-invasive) on event risks after PCI with contemporary drug-eluting stents. This post-hoc analysis pooled 3-year patient-level data of PCI all-comer patients living in the eastern Netherlands, previously treated for PADs. PADs included symptomatic atherosclerotic lesion in the lower or upper extremities; carotid or vertebral arteries; mesenteric arteries or aorta. Invasive PADs treatment comprised endarterectomy, bypass surgery, percutaneous transluminal angioplasty, stenting or amputation; non-invasive treatment consisted of medication and participation in exercise programs. Primary endpoint was (coronary) target vessel failure: composite of cardiac mortality, target vessel-related myocardial infarction, or clinically indicated target vessel revascularization. Of 461 PCI patients with PADs, information on PADs treatment was available in 357 (77.4%) patients; 249 (69.7%) were treated invasively and 108 (30.3%) non-invasively. Baseline and PCI procedural characteristics showed no between-group difference. Invasiveness of PADs treatment was not associated with adverse event risks, including target vessel failure (20.5% vs. 16.0%; HR: 1.30, 95%-CI 0.75–2.26, p = 0.35), major adverse cardiac events (23.3% vs. 20.4%; HR: 1.16, 95%-CI 0.71–1.90, p = 0.55), and all-cause mortality (12.1% vs. 8.3%; HR: 1.48, 95%-CI 0.70–3.13, p = 0.30). In PADs patients participating in PCI trials, we found no significant relation between the invasiveness of previous PADs treatment and 3-year outcome after PCI. Consequently, high-risk PCI patients can be identified by consulting medical records, searching for PADs, irrespective of the invasiveness of PADs treatment. Graphical abstract: (Figure presented.) Comparison of patients with non-invasive and invasive PADs treatment. PADs peripheral arterial disease, PCI percutaneous coronary intervention.</p
Stabilized immersed isogeometric analysis for the Navier-Stokes-Cahn-Hilliard equations, with applications to binary-fluid flow through porous media
Binary-fluid flows can be modeled using the Navier-Stokes-Cahn-Hilliard
equations, which represent the boundary between the fluid constituents by a
diffuse interface. The diffuse-interface model allows for complex geometries
and topological changes of the binary-fluid interface. In this work, we propose
an immersed isogeometric analysis framework to solve the
Navier-Stokes-Cahn-Hilliard equations on domains with geometrically complex
external binary-fluid boundaries. The use of optimal-regularity B-splines
results in a computationally efficient higher-order method. The key features of
the proposed framework are a generalized Navier-slip boundary condition for the
tangential velocity components, Nitsche's method for the convective
impermeability boundary condition, and skeleton- and ghost-penalties to
guarantee stability. A binary-fluid Taylor-Couette flow is considered for
benchmarking. Porous medium simulations demonstrate the ability of the immersed
isogeometric analysis framework to model complex binary-fluid flow phenomena
such as break-up and coalescence in complex geometries
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