1,498 research outputs found
Beyond technology and finance: pay-as-you-go sustainable energy access and theories of social change
Two-thirds of people in sub-Saharan Africa lack access to electricity, a precursor of poverty reduction and development. The international community has ambitious commitments in this regard, e.g. the UN's Sustainable Energy for All by 2030. But scholarship has not kept up with policy ambitions. This paper operationalises a sociotechnical transitions perspective to analyse for the first time the potential of new, mobileenabled, pay-as-you-go approaches to financing sustainable energy access, focussing on a case study of pay-as-you-go approaches to financing solar home systems in Kenya. The analysis calls into question the adequacy of the dominant, two-dimensional treatment of sustainable energy access in the literature as a purely financial/technology, economics/ engineering problem (which ignores sociocultural and political considerations) and demonstrates the value of a new research agenda that explicitly attends to theories of social change â even when, as in this paper, the focus is purely on finance. The paper demonstrates that sociocultural considerations cut across the literature's traditional two-dimensional analytic categories (technology and finance) and are material to the likely success of any technological or financial intervention. It also demonstrates that the alignment of new payas- you-go finance approaches with existing sociocultural practices of paying for energy can explain their early success and likely longevity relative to traditional finance approaches
An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris
The asymptotic giant branch (AGB) star R Sculptoris (R Scl) is one of the
most extensively studied stars on the AGB. R Scl is a carbon star with a
massive circumstellar shell () which
is thought to have been produced during a thermal pulse event years
ago. To study the thermal dust emission associated with its circumstellar
material, observations were taken with the Faint Object InfraRed CAMera for the
SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 m. Maps of
the infrared emission at these wavelengths were used to study the morphology
and temperature structure of the spatially extended dust emission. Using the
radiative transfer code DUSTY and fitting the spatial profile of the emission,
we find that a geometrically thin dust shell cannot reproduce the observed
spatially resolved emission. Instead, a second dust component in addition to
the shell is needed to reproduce the observed emission. This component, which
lies interior to the dust shell, traces the circumstellar envelope of R Scl. It
is best fit by a density profile with where
and dust mass of
. The strong departure from an
law indicates that the mass-loss rate of R Scl has not been constant.
This result is consistent with a slow decline in the post-pulse mass-loss which
has been inferred from observations of the molecular gas.Comment: 10 pages, 10 figures, accepted to Ap
The Extremal Structure Of Locally Compact Convex Sets
Let X be a locally compact closed convex subset of a locally convex Hausdorff topological linear space E. Then every exposed point of X is strongly exposed. The definitions of denting (strongly extreme) ray and strongly exposed ray are given for convex subsets of E. If X does not contain a line, then every extreme ray is strongly extreme and every exposed ray is strongly exposed. An example is given to show that the hypothesis that X be locally compact is necessary in both cases. © 1976 Pacific Journal of Mathematics. All rights reserved
Giant Pulses with Nanosecond Time Resolution detected from the Crab Pulsar at 8.5 and 15.1 GHz
We present a study of shape, spectra and polarization properties of giant
pulses (GPs) from the Crab pulsar at the very high frequencies of 8.5 and 15.1
GHz. Studies at 15.1 GHz were performed for the first time. Observations were
conducted with the 100-m radio telescope in Effelsberg in Oct-Nov 2007 at the
frequencies of 8.5 and 15.1 GHz as part of an extensive campaign of
multi-station multi-frequency observations of the Crab pulsar. A selection of
the strongest pulses was recorded with a new data acquisition system, based on
a fast digital oscilloscope, providing nanosecond time resolution in two
polarizations in a bandwidth of about 500 MHz. We analyzed the pulse shapes,
polarisation and dynamic spectra of GPs as well as the cross-correlations
between their LHC and RHC signals. No events were detected outside main pulse
and interpulse windows. GP properties were found to be very different for GPs
emitted at longitudes of the main pulse and the interpulse. Cross-correlations
of the LHC and RHC signals show regular patterns in the frequency domain for
the main pulse, but these are missing for the interpulse GPs. We consider
consequences of application of the rotating vector model to explain the
apparent smooth variation in the position angle of linear polarization for main
pulse GPs.
We also introduce a new scenario of GP generation as a direct consequence of
the polar cap discharge. We find further evidence for strong nano-shot
discharges in the magnetosphere of the Crab pulsar. The repetitive frequency
spectrum seen in GPs at the main pulse phase is interpreted as a diffraction
pattern of regular structures in the emission region. The interpulse GPs
however have a spectrum that resembles that of amplitude modulated noise.
Propagation effects may be the cause of the differences.Comment: Astronomy & Astrophysics (accepted
Statistical properties of giant pulses from the Crab pulsar
We have studied the statistics of giant pulses from the Crab pulsar for the
first time with particular reference to their widths. We have analyzed data
collected during 3.5 hours of observations conducted with the Westerbork
Synthesis Radio Telescope operated in a tied-array mode at a frequency of 1200
MHz. The PuMa pulsar backend provided voltage recording of X and Y linear
polarization states in two conjugate 10 MHz bands. We restricted the time
resolution to 4 microseconds to match the scattering on the interstellar
inhomogeneities. In total about 18000 giant pulses (GP) were detected in full
intensity with a threshold level of 6 sigma. Cumulative probability
distributions (CPD) of giant pulse energies were analyzed for groups of GPs
with different effective widths in the range 4 to 65 microseconds. The CPDs
were found to manifest notable differences for the different GP width groups.
The slope of a power-law fit to the high-energy portion of the CPDs evolves
from -1.7 to -3.2 when going from the shortest to the longest GPs. There are
breaks in the CPD power-law fits indicating flattening at low energies with
indices varying from -1.0 to -1.9 for the short and long GPs respectively. The
GPs with a stronger peak flux density were found to be of shorter duration. We
compare our results with previously published data and discuss the importance
of these peculiarities in the statistical properties of GPs for the heoretical
understanding of the emission mechanism responsible for GP generation.Comment: 5 pages, 2 figures. Accepted by Astronomy and Astrophysic
Crab pulsar giant pulses: Simultaneous radio and GRO observations
Observations are reported of the Crab pulsar made at radio frequencies concurrent with Oriented Scintillation Spectrometer Experiment (OSSE) observations from 15 to 27 May 1991. Using the 43 m telescope at Green Bank at 0.8 and 1.4 GHz, samples were made continuously for 10 hrs/day at intervals of 100 to 300 microsecs. The analysis of the radio data includes calculation of histograms of pulse intensities, absolute timing to about 20 microsec precision, and characterization of intensity variations on time scales from the 33 ms spin period to days. The most detailed analysis is presented made of giant pulses. The ultimate goal is to bin the radio data into giant and nongiant pulses and to form average waveforms of OSSE data for the corresponding pulse periods. A test is done to see whether the violet radio fluctuations (which are not seen in other radio pulsars to the same degree) are correlated with low energy gamma rays, yielding constraints on the radio coherence mechanism and the steadiness of the electron-positron outflow in the magnetosphere. Timing analysis of the radio data provides a well defined ephemeris over the specified range of epochs. The gamma ray pulse phase was predicted with an error of less than 70 microsecs
Scattering and Diffraction in Magnetospheres of Fast Pulsars
We apply a theory of wave propagation through a turbulent medium to the
scattering of radio waves in pulsar magnetospheres. We find that under
conditions of strong density modulation the effects of magnetospheric
scintillations in diffractive and refractive regimes may be observable. The
most distinctive feature of the magnetospheric scintillations is their
independence on frequency.
Results based on diffractive scattering due to small scale inhomogeneities
give a scattering angle that may be as large as 0.1 radians, and a typical
decorrelation time of seconds.
Refractive scattering due to large scale inhomogeneities is also possible,
with a typical angle of radians and a correlation time of the order
of seconds. Temporal variation in the plasma density may also result
in a delay time of the order of seconds. The different scaling of the
above quantities with frequency may allow one to distinguish the effects of
propagation through a pulsar magnetosphere from the interstellar medium. In
particular, we expect that the magnetospheric scintillations are relatively
more important for nearby pulsars when observed at high frequencies.Comment: 19 pages, 1 Figur
The Medication Adherence Report Scale (MARS-5): a measurement tool for eliciting patientsâ reports of non-adherence
Aims:
This study aimed to develop a questionnaire measure of patients' adherence to medications to elicit patients' report of medication use. The reliability and validity were assessed in patients with hypertension. Additional analyses were performed on other patient groups.
Methods:
Using a crossâsectional study design, a 10âitem version of the Medication Adherence Report Scale (MARS)© Professor Rob Horne was piloted in two samples of patients receiving treatment for hypertension (n=50 + 178), asthma (n=100) or diabetes (n=100) at hospital outpatient or community clinics in London and the SouthâEast of England. Following principal components analysis, five items were retained to form the âMARSâ5'©Professor Rob Horne. Evaluation comprised internal reliability, testâretest reliability, criterionârelated validity (relationship with blood pressure control) and construct validity (relationship with patients' beliefs about medicines).
Results:
The MARSâ5 demonstrated acceptable reliability (internal and testâretest) and validity (criterionârelated and construct validity). Internal reliability (Cronbach's α) ranged from 0.67 to 0.89 across all patient groups; testâretest reliability (Pearson's r) was 0.97 in Hypertension. Criterionârelated validity was established with more adherent hypertension patients showing better bloodâpressure control (Ï2=4.24, df=1, p<0.05). Construct validity with beliefs about medicines was demonstrated with higher adherence associated with stronger beliefs in treatment necessity, and lower concerns.
Conclusions:
The MARSâ5 performed well on several psychometric indicators. It shows promise as an effective selfâreport tool for measuring patients' reports of their medication use across a range of health conditions
Phase and Intensity Distributions of Individual Pulses of PSR B0950+08
The distribution of the intensities of individual pulses of PSR B0950+08 as a
function of the longitudes at which they appear is analyzed. The flux density
of the pulsar at 111 MHz varies strongly from day to day (by up to a factor of
13) due to the passage of the radiation through the interstellar plasma
(interstellar scintillation). The intensities of individual pulses can exceed
the amplitude of the mean pulse profile, obtained by accumulating 770 pulses,
by more than an order of magnitude. The intensity distribution along the mean
profile is very different for weak and strong pulses. The differential
distribution function for the intensities is a power law with index n = -1.1 +-
0.06 up to peak flux densities for individual pulses of the order of 160 Jy
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