3,477 research outputs found
Improving the Tanzanian-Mombasa cross-border tomato product chain: a study of Mombasa tomato market : draft report
The study of Mombasa tomato market is part of the project “Development of Commercial Field Vegetable Production, Distribution and Marketing for the East African Market”. The project is implementing a pilot activity on improving crossborder tomato chains from Ngarenanyuki, Tanzania, to Mombasa, Kenya. The overall objective of the study was to assess the requirements, institutional setting and current supply issues of the Mombasa tomato market and to describe the supply chain logistics and characteristics
The yellow hypergiants HR 8752 and rho Cassiopeiae near the evolutionary border of instability
High-resolution near-ultraviolet spectra of the yellow hypergiants HR 8752
and rho Cassiopeiae indicate high effective temperatures placing both stars
near the T_eff border of the ``yellow evolutionary void''. At present, the
temperature of HR 8752 is higher than ever. For this star we found
Teff=7900+-200 K, whereas rho Cassiopeiae has Teff=7300+-200 K. Both, HR 8752
and rho Cassiopeiae have developed strong stellar winds with Vinf ~ 120 km/s
and Vinf ~ 100 km/s, respectively. For HR 8752 we estimate an upper limit for
the spherically symmetric mass-loss of 6.7X10^{-6}M_solar/yr. Over the past
decades two yellow hypergiants appear to have approached an evolutionary phase,
which has never been observed before. We present the first spectroscopic
evidence of the blueward motion of a cool super/hypergiant on the HR diagram.Comment: 13 pages including 3 figures. Accepted for publication in ApJ Letter
Crossing the `Yellow Void' -- Spatially Resolved Spectroscopy of the Post- Red Supergiant IRC+10420 and Its Circumstellar Ejecta
IRC +10420 is one of the extreme hypergiant stars that define the empirical
upper luminosity boundary in the HR diagram. During their post--RSG evolution,
these massive stars enter a temperature range (6000-9000 K) of increased
dynamical instability, high mass loss, and increasing opacity, a
semi--forbidden region, that de Jager and his collaborators have called the
`yellow void'. We report HST/STIS spatially resolved spectroscopy of IRC +10420
and its reflection nebula with some surprising results. Long slit spectroscopy
of the reflected spectrum allows us to effectively view the star from different
directions. Measurements of the double--peaked Halpha emission profile show a
uniform outflow of gas in a nearly spherical distribution, contrary to previous
models with an equatorial disk or bipolar outflow. Based on the temperature and
mass loss rate estimates that are usually quoted for this object, the wind is
optically thick to the continuum at some and possibly all wavelengths.
Consequently the observed variations in apparent spectral type and inferred
temperature are changes in the wind and do not necessarily mean that the
underlying stellar radius and interior structure are evolving on such a short
timescale. To explain the evidence for simultaneous outflow and infall of
material near the star, we propose a `rain' model in which blobs of gas
condense in regions of lowered opacity outside the dense wind. With the
apparent warming of its wind, the recent appearance of strong emission, and a
decline in the mass loss rate, IRC +10420 may be about to shed its opaque wind,
cross the `yellow void', and emerge as a hotter star.Comment: To appear in the Astronomical Journal, August 200
Accepting or declining dialysis: considerations taken into account by elderly patients with end-stage renal disease
BACKGROUND: Elderly patients with end-stage renal disease have to make a difficult decision whether or not to start dialysis. This study explores the considerations taken into account by these patients in decision-making regarding renal replacement therapy. METHOD: In-depth interviews were conducted to gain an enhanced understanding of the considerations in treatment decision-making. Fourteen patients aged 65 years or older participated in the interviews, of whom 8 patients had made the decision to start, and 6 patients the decision to decline, dialysis. RESULTS: All participating patients had a variety of health problems, but appeared to have normal cognitive functions. Patients who declined dialysis were older and more often men and widow(er)s compared with patients who accepted dialysis. Patients chose to start dialysis because they enjoyed life, were not prepared to face the end of life, felt they had no other choice or had care-giving responsibilities for family members. Patients declined dialysis because of the speculated loss of autonomy, their age-associated decrease in vitality, distance from dialysis center and reluctance to think about the future. CONCLUSION: Results suggest that patients' decisions to decline or accept dialysis are not based on the effectiveness of the treatment, but rather on personal values, beliefs and feelings toward life, suffering and death, and the expected difficulties in fitting the treatment into their life
Delayed diagnosis of neuroschistosomiasis in a non-endemic country: A tertiary referral centre experience
BACKGROUND: Neuroschistosomiasis is a severe complication of schistosomiasis, triggered by the local immune reaction to egg deposition, with spinal cord involvement the most well recognised form. Early treatment with praziquantel and high dose steroids leads to a reduction of neurological sequelae. The rarity of this condition in returning travellers to high income countries can result in delayed diagnosis and treatment. We aimed to evaluate the diagnosis and management of neuroschistosomiasis in a UK national referral centre. MATERIALS AND METHODS: A retrospective review of confirmed clinical cases of spinal schistosomiasis referred to the Hospital for Tropical Diseases, UK, between January 2016 and January 2020 was undertaken. Electronic referral records were interrogated and patient demographic, clinical, laboratory, and radiological data collected. RESULTS: Four cases of neuroschistosomiasis were identified. The median age at diagnosis was 28 (range 21 to 50) with three male patients. All patients had epidemiological risk factors for schistosomiasis based on travel history and freshwater exposure; two in Uganda (River Nile), one in Malawi and one in Nigeria. All patients presented with features of transverse myelitis including back pain, leg weakness, paraesthesia and urinary dysfunction. The mean time from presentation to health services to definitive treatment was 42.5 days (range 16–74 days). Diagnosis was confirmed with CSF serology for schistosomiasis in all cases. Radiological features on MRI spine included enhancement focused predominantly in the lower thoracic spinal cord in three cases and the conus in one patient. All patients received a minimum of three days of oral praziquantel and high dose steroids. At three-month follow-up, one patient had complete resolution of symptoms and three had residual deficit; one patient was left with urinary and faecal incontinence, another had urinary retention, and the final patient has persistent leg pains and constipation. CONCLUSION: We observed a marked delay in diagnosis of neuroschistosomiasis in a non-endemic country. We advocate undertaking a thorough travel history, early use of imaging and CSF schistosomal serology to ensure early diagnosis of neuroschistosomiasis in patients presenting with consistent symptoms. If schistosomal diagnostics are not immediately available, presumptive treatment under the guidance of a tropical medicine specialist should be considered to minimize the risk of residual disability. We advocate for consensus guidelines to be produced and reporting to be performed in a uniform way for patients with spinal schistosomiasis
Recent Outbursts from the Transient X-Ray Pulsar Cep X-4 (GS 2138+56)
We report on X-ray observations of the 66 s period transient X-ray pulsar Cep
X-4 (GS 2138+56) with the Burst and Transient Source Experiment (BATSE) on the
Compton Gamma-Ray Observatory (CGRO) and with the Rossi X-ray Timing Explorer
(RXTE). Two outbursts from Cep X-4 were observed with BATSE in 1993 June-July
and 1997 July. Pulse frequencies of 15.0941 +/- 0.0002 mHz on 1993 June 25 (MJD
49,163) and 15.0882 +/- 0.0002 mHz on 1997 July 12 (MJD 50,641) were each
measured from 2 day spans of BATSE data near each outburst's peak. Cep X-4
showed an average spin down rate of (-4.14 +/- 0.08)*10^(-14) Hz/s between the
1993 and 1997 outbursts. After BATSE could no longer detect Cep X-4, public
observations were performed on 1997 July 18 & 25 with the Proportional Counter
Array (PCA) on RXTE. A pulse frequency of 15.088 +/- 0.004 mHz was measured
from observations on 1997 July 18 (MJD 50,647). Significant aperiodic noise,
with an rms variance of ~18% in the frequency range 0.01-1.0 Hz was observed on
both days. Energy and intensity dependent pulse shape variations were also seen
in these data. Recently published optical observations associate Cep X-4 with a
Be companion star. If all 4 outbursts observed from Cep X-4 are assumed to
occur at the same orbital phase, we find that the orbital period is between 23
days and 147.3 days.Comment: 19 pages (LaTeX) including 9 figures. Accepted for publication in the
Astrophysical Journa
Evolution of 3-9 Mo Stars for Z=0.001 - 0.03 and Metallicity Effects on Type Ia Supernovae
Recent observations have revealed that Type Ia supernovae (SNe Ia) are not
perfect standard candles but show some variations in their absolute magnitudes,
light curve shapes, and spectra. The C/O ratio in the SNe Ia progenitors (C-O
white dwarfs) may be related to this variation. In this work, we systematically
investigate the effects of stellar mass (M) and metallicity (Z) on the C/O
ratio and its distribution in the C-O white dwarfs by calculating stellar
evolution from the main-sequence through the end of the second dredge-up for
M=3-9 Mo and Z=0.001-0.03. We find that the total carbon mass fraction just
before SN Ia explosion varies in the range 0.36 -- 0.5. We also calculate the
metallicity dependence of the main-sequence-mass range of the SN Ia progenitor
white dwarfs. Our results show that the maximum main-sequence mass to form C-O
white dwarfs decreases significantly toward lower metallicity, and the number
of SN Ia progenitors may be underestimated if metallicity effectis neglected.
We discuss the implications of these results on the variation of SNe Ia,
determination of cosmological parameters, luminosity function of white dwarfs,
and the galactic chemical evolution.Comment: Added references and corrected typos. To appear in the Astrophysical
Journal 1999 March 10 issu
The peculiar B-type supergiant HD327083
Coude spectroscopic data of a poorly-studied peculiar supergiant, HD327083,
are presented. Halpha and Hbeta line profiles have been fitted employing a
non-LTE code adequate for spherically expanding atmospheres. Line fits lead to
estimates of physical parameters. These parameters suggest that HD327083 may be
close to the Luminous Blue Variable phase but it is also possible that it could
be a B[e] Supergiant.Comment: 4 pages, 4 figures, Accepted for publication in A&A Lette
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