1,488 research outputs found
Numerical Simulations of Pinhole and Single Mode Fibre Spatial Filters for Optical Interferometers
We use a numerical simulation to investigate the effectiveness of pinhole
spatial filters at optical/IR interferometers and to compare them with
single-mode optical fibre spatial filters and interferometers without spatial
filters. We show that fringe visibility measurements in interferometers
containing spatial filters are much less affected by changing seeing conditions
than equivalent measurements without spatial filters. This reduces visibility
calibration uncertainties, and hence can reduce the need for frequent
observations of separate astronomical sources for calibration of visibility
measurements. We also show that spatial filters can increase the
signal-to-noise ratios of visibility measurements and that pinhole filters give
signal-to-noise ratios within 17% of values obtained with single-mode fibres
for aperture diameters up to 3r_0. Given the simplicity of the use of pinhole
filters we suggest that it represents a competitive, if not optimal, technique
for spatial filtering in many current and next generation interferometers.Comment: 7 pages, 7 postscript figures. Accepted by MNRA
Iodine in the nutrition of sheep. Final report
1. Two groups of 10 merino ewes were fed the same adequate
basal ration with the exception that one group received an addition of 0.05 gms. each daily of potassium iodide.
2. A slight depression of weight and greater irregularity in
regard to the reproduction was shown by the group that received the iodine supplement. The detrimental effects, however, were not as marked as recorded in previous work where other deficiencies, especially vitamin A, undoubtedly exercised an aggravating influence on reproductive abnormalities.
3. The indiscriminate use of iodine supplements for sheep is
not recommended.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Studies in mineral metabolism. XXXIII. Iodine in the nutrition of sheep. Second report
1. Data are presented on the effect of KI in the feed of 40 merino
ewes for a period of 30 months.
2. The quantities of KI given per sheep daily were 0.002 grm.,
0.02 grm., 0.06 grm. in three groups respectively, while one group
received no KI and acted as controls.
3. Observations were made on the food consumption, weight
increase, wool production, reproduction and health of the animals
for the full period of the experiment. Further, observations were
made on the oestrus cycle of the ewes and no significant group
differences were observed.
4. The animals were fed in individual feeding boxes except the
hay, which was given ad lib.
5. It is concluded that neither the small dose nor the bigger
quantities of KI fed had any visible effect on the weights, wool
production and reproduction of the animals.
6. It is also pointed out that the ill effects ascribed to iodide
feeding in the earlier work were apparently aggravated by another
deficiency, the possibility of the existence of which was not considered in the earlier work, viz. vitamin A.
7. It is concluded that the addition of KI to sheep licks is unwarranted,
may even produce visibly detrimental effects under conditions
of drought, when a vitamin A shortage may exist, and is to be
discouraged in practical farming unless there is reason for believing
that an iodine deficiency exists.
8. Further work on the effects of iodine feeding under practical
conditions, as for instance during severe droughts when apparently
detrimental effects may be experienced, is being undertaken.
The writers wish to acknowledge gratefully the assistance of
Mr. A. P. Malan, Statistician, in dealing with the results given in
the lambing charts.The articles have been scanned in colour with a HP Scanjet 5590;300dpi.
adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Experimental osteodystrophic diseases in goats
(1) Starvation proved to be an important factor in the development
of bone atrophy in the case of two kids which received a ration
low in calcium and high in phosphorus, where the CaO:Pâ‚‚Oâ‚… ratio
was wide.
(2) Clinical symptoms of rickets were observed only in a case
where the phosphorus intake was low and that of calcium high, with
a wide ratio.
(3) When the calcium and phosphorus intakes were both low,
their ratio being normal, the histological examination of the bone
showed the presence of rickets.
(4) The inhibition of normal growth, due to semi-starvation,
resulted in the eventual development of bone atrophy and not
osteofibrosis. Even rickets, which is more easily produced than
osteofibrosis, in time gives way to atrophy in the presence of
cessation of bone growth.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
A field evaluation of the BGI and cowl type gravimetric samplers
After initial studies by the CSIR indicating that a discrepancy
exists in the dust concentration results between gravimetric dust
samplers, alternative instruments or methods were sought. In
the study that followed; it was recommended by the HSL in the
UK that a cowl arrangement, together with a sampling rate
equivalent to the CEN / ISO standard, be used to minimize over
sampling. As such CEN/ISO recommended sampling rate of 2.2
l/min was used for the first time in South African mines. A BGIstainless
steel cyclone sampler and a Higgins Dewell type
sampler with a cowl arrangement were used in the study.
Implementation of the recommended changes to samplers and
the flow rate will interrupt the continuity of monitoring data built
up over the years, but they will raise South African dust measurements
to international standards. Although extensive work has
been carried out on the use of cyclones, most of the previous
studies were carried out in the laboratory, which have an advantage
over the extremely difficult conditions in underground coal
mines. This paper describes the field results from the two gravimetric
samplers tested underground.The authors would like to acknowledge the
financial support of CSIR-Miningtek and SIMRAC.CSIR-Miningtek and SIMRAC.http://www.mvssa.co.zaam2017Mining Engineerin
Studies in mineral metabolism XXXV. The role of iodine in the nutrition of sheep
When the daily ration of Merino ewes contained 0.05 gm. KI for a period of about twelve months no effects were observed in bodyweight and food consumption. Reproduction was, however, abnormal in all the groups receiving the KI supplement, the effects of which were more pronouncedly deleterious in sheep on a carotene low diet than when 200 grm. greenfeed were supplied daily. The response to increased protein feeding in the form of bloodmeal was marked by the detrimental effect of KI on reproduction. As all the rations can easily be improved both in quality and palatability it cannot be inferred that the quantity of KI given will affect reproduction in sheep adversely under ideal feeding conditions. The conclusion is justified, however, that when greenfeed is absent or inadequate as frequently happens in practice good quality protein is not available and the incorporation of KI in sheep licks is distinctly dangerous and may even cause losses due to abnormal reproduction.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
Study protocol: a randomised controlled trial on the clinical effects of levothyroxine treatment for subclinical hypothyroidism in people aged 80 years and over
Background:
Subclinical hypothyroidism is common in older people and its contribution to health and disease needs to be elucidated further. Observational and clinical trial data on the clinical effects of subclinical hypothyroidism in persons aged 80 years and over is inconclusive, with some studies suggesting harm and some suggesting benefits, translating into equipoise whether levothyroxine therapy provides clinical benefits. This manuscript describes the study protocol for the Institute for Evidence-Based Medicine in Old Age (IEMO) 80-plus thyroid trial to generate the necessary evidence base.
Methods:
The IEMO 80-plus thyroid trial was explicitly designed as an ancillary experiment to the Thyroid hormone Replacement for Untreated older adults with Subclinical hypothyroidism randomised placebo controlled Trial (TRUST) with a near identical protocol and shared research infrastructure. Outcomes will be presented separately for the IEMO and TRUST 80-plus groups, as well as a pre-planned combined analysis of the 145 participants included in the IEMO trial and the 146 participants from the TRUST thyroid trial aged 80 years and over.
The IEMO 80-plus thyroid trial is a multi-centre randomised double-blind placebo-controlled parallel group trial of levothyroxine treatment in community-dwelling participants aged 80 years and over with persistent subclinical hypothyroidism (TSH ≥4.6 and ≤ 19.9 mU/L and fT4 within laboratory reference ranges). Participants are randomised to levothyroxine 25 or 50 micrograms daily or matching placebo with dose titrations according to TSH levels, for a minimum follow-up of one and a maximum of three years.
Primary study endpoints: hypothyroid physical symptoms and tiredness on the thyroid-related quality of life patient-reported outcome (ThyPRO) at one year. Secondary endpoints: generic quality of life, executive cognitive function, handgrip strength, functional ability, blood pressure, weight, body mass index, and mortality. Adverse events will be recorded with specific interest on cardiovascular endpoints such as atrial fibrillation and heart failure.
Discussion:
The combined analysis of participants in the IEMO 80-plus thyroid trial with the participants aged over 80 in the TRUST trial will provide the largest experimental evidence base on multimodal effects of levothyroxine treatment in 80-plus persons to date
Studies in mineral metabolism. XXXII. The effect of different forms of sulphur in the diet upon the growth and wool production of sheep
(1) Details are presented of an experiment on the effects of sulphur and of compounds containing sulphur on the food consumption, weight increase, wool yield and disease of young wethers kept on a production ration for two years.
(2) The sheep were fed in individual feeding boxes except for the hay which was given ad lib.
(3) The supplements given were dosed daily except Sundays and were given as follows:-Group I: No supplement.
Group II: Cystine.
Group III: Sulphates.
Group IV: KCNS.
Group V: 5 gm. sulphur.
Group VI: •12 gm. sulphur.
(4) No significant effects of the supplements on the sheep could be detected after 12 months' supplementary feeding nor did the experimental groups differ significantly from the control group at the end of the experimental period.
(5) The supplement of cystine had no effect on the quantity of wool produced.
(6) The mortality and disease due to the presence of urinary calculi were apparently not associated with the supplements.
(7) The analyses of the wool will be reported on in due course.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format
The implementation of wideband 90° hybrids on non-optimal substrates
A new technique to implement wideband 90° hybrid coupling profiles
on non-optimal substrate configurations is presented. The technique
uses an impedance taper over the whole length of the hybrid to remove
the restriction of a substrate defined maximum coupling coefficient at
crossover, thus resulting in much more flexibility for the implementation
of hybrids on integrated printed circuit boards. The choice of board
thicknesses and material type no longer needs to be dominated by the
hybrid, but can be optimized for other components or priorities. The
flexibility provided by the technique is shown in the implementation of
a 2–18 GHz hybrid on a large range of substrate thicknesses as well
as on a non-optimal substrate material, for which acceptable measured
performance is still obtained.http://wileyonlinelibrary.com/iet-elam2022Electrical, Electronic and Computer Engineerin
Experimental simulation of retrodirective cross-eye jamming
Experimental measurements that accurately simulate the
effect of a retrodirective cross-eye jammer on a monopulse radar
are described. The accuracy of a recently published extended
analysis of retrodirective cross-eye jamming and the limitations
of the conventional phase-front analysis of cross-eye jamming are
illustrated by the experiments.The Armaments Corporation of South Africa (Armscor) and the National Research Foundation (NRF).http://ieeexplore.ieee.org/ai201
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