5,502 research outputs found
Space VLBI Observations Show in the Quasar NRAO 530
We present here space-based VLBI observations with VSOP and a southern
hemisphere ground array of the gamma-ray blazar NRAO 530 at 1.6 GHz and 5 GHz.
The brightness temperature of the core at 1.6 GHz is K. The
size is near the minimum observable value in the direction of NRAO~530 due to
interstellar scattering. The 5 GHz data show a single component with a
brightness temperature of K, significantly in excess of
the inverse Compton limit and of the equipartition brightness temperature limit
(Readhead 1994). This is strong evidence for relativistic motion in a jet
requiring model-dependent Doppler boosting factors in the range 6 to 60. We
show that a simple homogeneous sphere probably does not model the emission
region accurately. We favor instead an inhomogeneous jet model with a Doppler
boosting factor of 15.Comment: 12 pages, 2 figures. Accepted for publication in ApJ Letter
Green Bank Telescope Observations of the Eclipse of Pulsar "A" in the Double Pulsar Binary PSR J0737-3039
We report on the first Green Bank Telescope observations at 427, 820 and 1400
MHz of the newly discovered, highly inclined and relativistic double pulsar
binary. We focus on the brief eclipse of PSR J0737-3039A, the faster pulsar,
when it passes behind PSR J0737-3039B. We measure a frequency-averaged eclipse
duration of 26.6 +/- 0.6 s, or 0.00301 +/- 0.00008 in orbital phase. The
eclipse duration is found to be significantly dependent on radio frequency,
with eclipses longer at lower frequencies. Specifically, eclipse duration is
well fit by a linear function having slope (-4.52 +/- 0.03) x 10^{-7}
orbits/MHz. We also detect significant asymmetry in the eclipse. Eclipse
ingress takes 3.51 +/- 0.99 times longer than egress, independent of radio
frequency. Additionally, the eclipse lasts (40 +/- 7) x 10^{-5} in orbital
phase longer after conjunction, also independent of frequency. We detect
significant emission from the pulsar on short time scales during eclipse in
some orbits. We discuss these results in the context of a model in which the
eclipsing material is a shock-heated plasma layer within the slower PSR
J0737-3039B's light cylinder, where the relativistic pressure of the faster
pulsar's wind confines the magnetosphere of the slower pulsar.Comment: 12 pages, 3 figure
Exercise-Induced Asthma Symptoms and Nighttime Asthma: Are They Similar to AHR?
Background. Asthma experienced during exercise and during the night is based on the presence of airway hyperresponsiveness (AHR). The aim of the present study was to examine whether AHR is a predictor of exercise-induced asthma (EIA) and nighttime symptoms. Material. We included 793 asthmatics subjects with symptoms and a positive asthma test.
Results. Mean (SD) FEV1 was 93% (15), 71% had rhinitis, and 62% had atopy. Both EIA and nighttime symptoms were associated with AHR; however, when including other factors of importance in a multivariate analysis, logRDR was eliminated, whereas FEV1% pred (P < .001), smoking (P < .05), atopy (P < .001), sex (P < .001), and treatment (P < .01) were associated with having EIA while dyspnoea (P < .001), cough (P < .001), and eosinophils (P < .01) were associated with frequent night symptoms. The risk of having nighttime awakenings due to asthma was more than twofold higher among those with EIA symptoms than among those without symptoms (OR (CI95%) 2.77 (2.0–3.8) (P < .001)). In Conclusion. EIA and night symptoms are associated with AHR, but other factors of importance eliminated this close association. Night asthma is more closely associated with airway inflammation than AHR
Through thick and thin: young people's affective geographies in Brussels' public space
Young people's interaction with place is not only a cognitive process of identification but also an affective relation. There has been plenty of research on young people and/in public space but few of those studies have taken such an affective layer of analysis into account. In this paper we aim to shed some light on young people's affective geographies through the concept of ‘thick places’ as it was proposed by Edward Casey (2001), building upon ethnographic research undertaken between 2013 and 2016 in Brussels. We argue that such a concept is only useful if we consider thickness not only as a reference to ‘warm’, ‘authentic’ or ‘intimate’ places but also as a term that takes the ‘normative architecture’ of place into account. We embed this claim in a discussion of affects, atmospheres and Peter Sloterdijk's notion of nomotop.info:eu-repo/semantics/acceptedVersio
SLT-VEGF Reduces Lung Metastases, Decreases Tumor Recurrence, and Improves Survival in an Orthotopic Melanoma Model
SLT-VEGF is a recombinant cytotoxin comprised of Shiga-like toxin (SLT) subunit A fused to human vascular endothelial growth factor (VEGF). It is highly cytotoxic to tumor endothelial cells overexpressing VEGF receptor-2 (VEGFR-2/KDR/Flk1) and inhibits the growth of primary tumors in subcutaneous models of breast and prostate cancer and inhibits metastatic dissemination in orthotopic models of pancreatic cancer. We examined the efficacy of SLT-VEGF in limiting tumor growth and metastasis in an orthotopic melanoma model, using NCR athymic nude mice inoculated with highly metastatic Line IV Cl 1 cultured human melanoma cells. Twice weekly injections of SLT-VEGF were started when tumors became palpable at one week after intradermal injection of 1 × 106 cells/mouse. Despite selective depletion of VEGFR-2 overexpressing endothelial cells from the tumor vasculature, SLT-VEGF treatment did not affect tumor growth. However, after primary tumors were removed, continued SLT-VEGF treatment led to fewer tumor recurrences (p = 0.007), reduced the incidence of lung metastasis (p = 0.038), and improved survival (p = 0.002). These results suggest that SLT-VEGF is effective at the very early stages of tumor development, when selective killing of VEGFR-2 overexpressing endothelial cells can still prevent further progression. We hypothesize that SLT-VEGF could be a promising adjuvant therapy to inhibit or prevent outgrowth of metastatic foci after excision of aggressive primary melanoma lesions
New Pulsars from an Arecibo Drift Scan Search
We report the discovery of pulsars J0030+0451, J0711+0931, and J1313+0931
that were found in a search of 470 square degrees at 430 MHz using the 305m
Arecibo telescope. The search has an estimated sensitivity for long period, low
dispersion measure, low zenith angle, and high Galactic latitude pulsars of ~1
mJy, comparable to previous Arecibo searches. Spin and astrometric parameters
for the three pulsars are presented along with polarimetry at 430 MHz. PSR
J0030+0451, a nearby pulsar with a period of 4.8 ms, belongs to the less common
category of isolated millisecond pulsars. We have measured significant
polarization in PSR J0030+0451 over more than 50% of the period, and use these
data for a detailed discussion of its magnetospheric geometry. Scintillation
observations of PSR J0030+0451 provide an estimate of the plasma turbulence
level along the line of sight through the local interstellar medium.Comment: 21 pages, 4 figures, Accepted for Publication in Ap
- …