53 research outputs found
Pulsar Magnetospheric Emission Mapping: Images and Implications of Polar-Cap Weather
The beautiful sequences of ``drifting'' subpulses observed in some radio
pulsars have been regarded as among the most salient and potentially
instructive characteristics of their emission, not least because they have
appeared to represent a system of subbeams in motion within the emission zone
of the star. Numerous studies of these ``drift'' sequences have been published,
and a model of their generation and motion articulated long ago by Ruderman &
Sutherland (1975); but efforts thus far have failed to establish an
illuminating connection between the drift phemomenon and the actual sites of
radio emission. Through a detailed analysis of a nearly coherent sequence of
``drifting'' pulses from pulsar B0943+10, we have in fact identified a system
of subbeams circulating around the magnetic axis of the star. A mapping
technique, involving a ``cartographic'' transform and its inverse, permits us
to study the character of the polar-cap emission ``map'' and then to confirm
that it, in turn, represents the observed pulse sequence. On this basis, we
have been able to trace the physical origin of the ``drifting-subpulse''
emission to a stably rotating and remarkably organized configuration of
emission columns, in turn traceable possibly to the magnetic polar-cap ``gap''
region envisioned by some theories.Comment: latex with five eps figure
Pulsar "Drifting"-Subpulse Polarization: No Evidence for Systematic Polarization-Angle Rotations
Polarization-angle density displays are given for pulsars B0809+74 and
B2303+30, which exhibit no evidence of the systematic polarization-angle
rotation within individual subpulses previously reported for these two stars.
The ``drifting'' subpulses of both pulsars exhibit strikingly linear and
circular polarization which appears to reflect the characteristics of two
nearly orthogonally polarized emission ``modes''--along which the severe
average-profile depolarization that is characteristic of their admixture at
comparable overall intensities.Comment: Accepted for publication in Astronomy & Astrophysic
A Novel Approach to Evaluating the Iron and Folate Status of Women of Reproductive Age in Uzbekistan after 3 Years of Flour Fortification with Micronutrients
Background: The Uzbekistan 1996 Demographic Health Survey reported 60.4% of women of reproductive age (WRA) had low hemoglobin concentrations (5 mg/L). Severe anemia was more prevalent among folate deficient than iron depleted WRA. Presence of UDM first grade flour or the grey loaf was reported in 71.3% of households. Among WRA, 32.1% were aware of UDM fortification; only 3.7% mentioned the benefits of fortification and 12.5% understood causes of anemia. Consumption of heme iron-containing food (91%) and iron absorption enhancers (97%) was high, as was the consumption of iron absorption inhibitors (95%). Conclusions/Significance: The NFFP coincided with a substantial decline in the prevalence of anemia. Folate deficiency was a stronger predictor of severe anemia than iron depletion. However, the prevalence of iron depletion was high, suggesting that women are not eating enough iron or iron absorption is inhibited. Fortified products were prevalent throughout Uzbekistan, though UDM flour must be adequately fortified and monitored in the future. Knowledge of fortification and anemia was low, suggesting consumer education should be prioritized
An Empirical Model for the Radio Emission from Pulsars
A model for slow radio pulsars is proposed which involves the entire
magnetosphere in the production of the observed radio emission. It is argued
that observations of pulsar profiles suggest that a feedback mechanism exists
between the star surface and the null charge surface, requiring particle flow
in both directions. In their flow to and from the surface the particles execute
an azimuthal drift around the magnetic pole, thereby creating a ring of
discrete `emission nodes' close to the surface. Motion of the nodes is observed
as the well-known subpulse `drift', but is interpreted here as a small residual
component of the real particle drift. The nodes can therefore move in either
direction, or even remain stationary. A precise fit is found for the pulsar
PSR0943+10. Azimuthal interactions between different regions of the
magnetosphere depend on the angle between the magnetic and rotation axes and
influence the conal type, as observed. The requirement of intermittent weak
pair-production in an outergap suggests a natural evolutionary link between
radio and gamma-ray pulsars.Comment: 17 pages 8 figure
Observations of Non-radial Pulsations in Radio Pulsars
We introduce a model for pulsars in which non-radial oscillations of high
spherical degree (l) aligned to the magnetic axis of a spinning neutron star
reproduce the morphological features of pulsar beams. In our model, rotation of
the pulsar carries a pattern of pulsation nodes underneath our sightline,
reproducing the longitude stationary structure seen in average pulse profiles,
while the associated time-like oscillations reproduce "drifting
subpulses"--features that change their longitude between successive pulsar
spins. We will show that the presence of nodal lines can account for observed
180 degree phase jumps in drifting subpulses and their otherwise poor phase
stability, even if the time-like oscillations are strictly periodic. Our model
can also account for the "mode changes" and "nulls" observed in some pulsars as
quasiperiodic changes between pulsation modes of different l or radial overtone
n, analogous to pulsation mode changes observed in oscillating white dwarf
stars. We will discuss other definitive and testable requirements of our model
and show that they are qualitatively supported by existing data. While
reserving judgment until the completion of quantitative tests, we are inspired
enough by the existing observational support for our model to speculate about
the excitation mechanism of the non-radial pulsations, the physics we can learn
from them, and their relationship to the period evolution of pulsars.Comment: 28 pages, 9 figures (as separate png files), Astrophysical Journal,
in pres
First national survey of anti-tuberculosis drug resistance in Azerbaijan and risk factors analysis.
SETTING: Civilian population of the Republic of Azerbaijan. OBJECTIVES: To determine patterns of anti-tuberculosis drug resistance among new and previously treated pulmonary tuberculosis (TB) cases, and explore their association with socio-demographic and clinical characteristics. DESIGN: National cross-sectional survey conducted in 2012-2013. RESULTS: Of 789 patients (549 new and 240 previously treated) who met the enrolment criteria, 231 (42%) new and 146 (61%) previously treated patients were resistant to any anti-tuberculosis drug; 72 (13%) new and 66 (28%) previously treated patients had multidrug-resistant TB (MDR-TB). Among MDR-TB cases, 38% of new and 46% of previously treated cases had pre-extensively drug-resistant TB (pre-XDR-TB) or XDR-TB. In previously treated cases, 51% of those who had failed treatment had MDR-TB, which was 15 times higher than in relapse cases (OR 15.2, 95%CI 6-39). The only characteristic significantly associated with MDR-TB was a history of previous treatment (OR 3.1, 95%CI 2.1-4.7); for this group, history of incarceration was an additional risk factor for MDR-TB (OR 2.8, 95%CI 1.1-7.4). CONCLUSION: Azerbaijan remains a high MDR-TB burden country. There is a need to implement countrywide control and innovative measures to accelerate early diagnosis of drug resistance in individual patients, improve treatment adherence and strengthen routine surveillance of drug resistance
Performance of a plastic scintillator developed using styrene monomer polymerization
This paper presents a newly developed plastic scintillator produced in
collaboration with Turkiye Energy, Nuclear and Mineral Research Agency
(TENMAK). The scintillator is manufactured using thermal polymerization of
commercially available styrene monomer. The absorption spectrum of the
scintillator exhibited two absorption bands at 225 nm and 340 nm, with an
absorption edge observed at 410 nm. The wavelength of the emitted light was
measured in the range of 400-800 nm, with a maximum intensity at 427 nm.
Monoenergetic electrons from the 137Cs source were used to evaluate the
characteristics of the new scintillator, particularly its light yield. As the
light readout the MAPD-3NM type silicon photomultiplier array (4 x 4) with an
active area of 15 x 15 mm2, assembled using single MAPDs with an active area of
3.7 x 3.7 mm2, was used. The light yield of the scintillator was determined to
be 6134 photons/MeV. In addition, the efficiency of the scintillator for gamma
rays with an energy of 662 keV was found to be approximately 1.8 %. A CmBe
neutron source was employed to evaluate its fast neutron detection performance.
However, neutron/gamma discrimination using pulse shape discrimination (charge
integration) method was not observed. The results demonstrate the potential of
a newly produced plastic scintillator for various applications, particularly in
radiation monitoring and detection systems.Comment: 7 pages, 7 figure
Toward An Empirical Theory of Pulsar Emission VIII: Subbeam Circulation and the Polarization-Modal Structure of Conal Beams
The average polarization properties of conal single and double profiles
directly reflect the polarization-modal structure of the emission beams which
produce them. These average properties require that the circulating subbeam
systems which produce conal beams entail paired PPM and SPM emission elements
which are offset from each other in both magnetic azimuth and magnetic
colatitude.
A clear delineation of the modal polarization topology of the conal beam
promises to address fundamental questions about the nature and origin of this
modal emission--and the modal parity at the outer beam edges is a fact of
considerable significance. The different angular dependences of the modal
``beamlets'' suggests that the polarization modes are generated via propagation
effects. This argument may prove much stronger if the modal emission is
fundamentally only partially polarized. Several theories now promise
quantitative comparison with the observations.Comment: Submitted to Astrophysical Journa
Reestablishing Stability and Avoiding a Credit Crunch: Comparing Different Bad Bank Schemes
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