3,401 research outputs found
The fate of legume seeds eaten by sheep from a Mediterranean grassland
No full textThe consumption of legume seed by grazing sheep was assessed in a Mediterranean grassland in north-west Syria, during the summers of 1986 and 1987. Large paddocks were also surveyed for the amount of legume seed in sheep faeces. The seed recovery of the most common legumes (Trifolium stellatum L., T. tomentosum L. and T. campestre Schreb.) was also investigated in a pen-feeding experiment, by feeding 150-200 g of clover pods to each of 10 sheep in a single meal. The percentage of hard seeds was assessed before and after passage of seeds through the sheep's alimentary tract.
When large numbers of legume seeds were present in the grassland, seed consumption was proportional to the stocking rates, but when small numbers were present (less than 2000-3000 seeds m-2) sheep ate proportionately fewer seed, because they were difficult to gather.
Sheep faeces collected from the grassland contained an average of 9.5 legume seeds per pellet. Seed recovery after controlled ingestion was 23, 36 and 59% of the number eaten, for T. stellatum, T. tomentosum and T. campestre, respectively; recovery was inversely proportional to seed size.
Ingestion reduced hardseededness, so that a greater proportion of the seeds were capable of germinating after ingestion
Coat thickness and hard seededness in some Medicago and Trifolium species
No full textThe seeds of three medics (Medicago orbicularis, M. rigidula and M. rotata) and three clovers (Trifolium steilatum, T. campestre and T. tomentosum) were collected from a pasture in north-west Syria on three occasions: immediately after seed set, at the end of the dry season, i.e. 4 months after seed set, and 16 months after seed set. Complete and sectioned seeds were observed with a scanning electron microscope. Morphological changes and differences in thickness of the seed coat were related to the hard-seededness of the samples collected in the seed bank before the onset of the rainy season. The morphology and structure of the seed coat of all six species were typical of papilionoid legumes. The species with the softest seeds (T. steilatum) showed a very thin and discontinuous cuticular layer at seed maturation (0.16 pm), while a thick and continuous cuticle (4.24 pm) was characteristic of the hardest-seeded species (M. orbicularis). The lens region of seed of all species except T. campestre was weakened after a few months in the field. This weakening was also found in seeds which were certainly hard, but the cracks in the lens region were apparently not deep enough to allow imbibition. Even when large areas of the palisade layer were removed from the lens region of seeds of M. rotata, this was not sufficient to permit water uptake. Differences in the seed coat thickness of the six species accounted for differences in seed dormancy only when seed mass was taken into account
Seed bank dynamics in a Mediterranean grassland.
No full textChanges in the seed bank, seedling emergence and plant density of the most common grass species, and all legume species, were monitored in a grassland in north Syria from October 1986 to May 1989.
The seed bank was greatest in May-June, following pasture maturity, then declined to its minimum in March-April. Losses of seeds during summer were mainly due to sheep grazing, while losses in winter and spring were mainly due to germination, although some seeds were eaten by soil fauna and some seeds died. The seed bank, particularly of the small-seeded species (Trifolium tomentosum and T. campestre) was greater under the high stocking rate than under the low stocking rate.
There was little seed carry-over of grasses from season to season (Avena spp. 5%, Heteranthelium piliferum 1%, Bromus spp. 0%), but seed carry-over was greater in legumes (Trifolium stellatum 27%, T. campestre 35%, and T. tomentosum 38%). Most seedlings emerged in the autumn, but emergence continued throughout the growing season. Plant density within each year reached a peak in January, declining as spring approached.
The ecological and agricultural importance of seed banks in native Mediterranean grasslands is discussed
Wavelength tunable 10-GHz 3-ps pulse source using a dispersion decreasing fiber-based nonlinear optical loop mirror
No full textWe experimentally demonstrate the use of a dispersion decreasing fiber (DDF)-based nonlinear optical loop mirror (NOLM) for the generation of wavelength tunable soliton-like pulses at a repetition rate of 10 GHz. We compress ~12 ps Gaussian pulses from an electro-absorption modulator (EAM) (followed by 125 m of DCF for preliminary linear dispersion compensation) into 3 ps pedestal-free pulses using both high-order soliton compression and nonlinear switching effects within an 8.5 km DDF-based loop mirror. The output pulses from the DDF-based NOLM show considerable pedestal reduction compared to those obtained by directly compressing the EAM seed pulses via a single passage through the DDF. Wavelength tuning of the compressed pulses over a ~15 nm bandwidth (from 1541 to 1556 nm) is demonstrated without a significant increase in pulse duration or degradation in pulse quality
Effects of season on the reproductive organ and plasma testosterone concentrations in guinea cocks (Numida meleagris)
No full textThe physiological basis of seasonal breeding in the guinea fowl (Numida meleagris) still remains unknown, despite the socioeconomic importance of these birds, particularly in Ghana. A study involving a total of 50 local guinea cocks was conducted, and documented gross anatomical and histological differences in the reproductive organs of breeding and non-breeding male guinea fowls. The study also compared peripheral testosterone concentrations in breeding and non-breeding cocks. Seasonal differences in variables measured were determined using two-tailed t-test/Mann-Whitney U-test. All comparisons were made at 5% level of significance. Breeding males had significantly (P = 0.000) higher anatomical biometric parameters than their non-breeding counterparts. Also, breeding birds had thicker (P = 0.000) phalli than their non-breeding counterparts. Histologically, regressing testis was characterized by the presence of sloughed off cells and increased debris in the tubular lumen and within the excurrent duct system, collapsed tubules and reduction in tubular lumen. Germ and Sertoli cell populations and nuclear diameters and actual seminiferous tubular diameter and length in regressing testes were significantly (P = 0.000) lower than in active testes. Leydig cell nuclear diameters and populations were also significantly (P = 0.000) reduced. Relative volume of seminiferous tubules in the testis, testicular sperm production/mg testis and per testis and peripheral testosterone concentrations were all higher (P < 0.05) in breeding than non-breeding testis. The ducts in the epididymal region also saw significant (P < 0.05) reductions in luminal diameters in non-breeding birds. Significant regression in anatomical and histological structures of the guinea cock reproductive tract occurred during the non-breeding season, and lower peripheral testosterone concentrations may be responsible for this phenomenon
Recovery and germination rates of seeds of Mediterranean medics and clovers offered to sheep at a single meal or continuously
No full textMeasurements were made of the recovery and germination rates of seed of eight species of annual medic (Medicago spp.) and three of clover (Trifolium spp.) after ingestion by sheep. Recovery of medic seed was measured as the number of seeds collected from faeces after feeding, in addition to a basal diet, either (i) 200 g of pods at a single meal, or (ii) a quantity of pods estimated to contain 30000 seeds at a single meal or (iii) 200 g of pods daily for 21 days. Only the first method was applied to the clovers. There were large differences (P < 0.001) in seed recovery between species, from < 2 % to nearly 20 % in medics, and up to 59 % in T. campestre, which has low single-seed mass. Although there was a curvilinear decrease in seed recovery as single-seed mass increased (r2 = 0.80), the high recovery of M. rotata, a fairly large-seeded species, suggests that there are important differences between species, irrespective of seed size. When 200 g of medic pods was offered to sheep at a single meal, mean seed recovery was slightly lower than when 200 g of medic pods was offered daily for 21 days. Seed recovery of medics was much higher (P < 0.001) when 30000 seeds were offered at one meal. Germination rate before ingestion was 1.9-6-5 % (P < 0.001) for hard-seeded medics and 2-7-9.7 % (P < 0.001) for clovers with low single-seed mass; passage through the digestive tract increased (P < 0.001) germination rate in both medics and clovers
Response of Mediterranean grassland to phosphate and stocking rates: biomass production and botanical composition
No full textThree rates of phosphate (0, 25, and 60 kg/ha P2O5) were applied phosphorus-deficient native grassland at Tel Hadya, in northern Syria, and biomass productivity, botanical composition and number of legume seeds in the soil were monitored for five seasons (1984/85-1988/89). The experiment was grazed at low (0.8 sheep/ha per year) and high (1.7 sheep/ha per year) stocking rates from the second to the fourth seasons of the experiment; in the fifth season, the low and high stocking rates were increased to 1.1 and 2.3 sheep/ha per year, respectively. The experimental site was typical of native grassland within the cereal zone of west Asia, where cropping is not possible because of shallow, stony soils and steep slopes.
The results showed that annual applications of phosphorus, even as low as 25 kg P2O5/ha, alleviated the deficiency in soil P and resulted in improved pasture production, even in dry years. Legume production showed the greatest response to P, increasing by 0.3-3 times the production of the control treatments. By the fifth season, legume seed mass had increased threefold and number of seeds sixfold in the P-treated plots, compared with the first season, while in the control plots there was little change. Rain-use efficiency on the P-treated plots was more than double that of the controls by the fourth and fifth seasons.
Practical application of the results depends on whether (i) legumes are as frequent in native grasslands, as a whole, as they are at Tel Hadya, (ii) the P deficiency observed at Tel Hadya is widespread, and (iii) grazing of communally owned grasslands can be controlled. It is suggested that all three criteria will often be fulfilled and, therefore, that grassland productivity in west Asia could be substantially increased. Furthermore, the results suggest that above-ground cover and soil organic matter will also increase after P application, both of which will help to reduce soil erosion and thereby increase the sustainability of livestock production in west Asia
Player agency in interactive narrative: audience, actor & author
No full textThe question motivating this review paper is, how can
computer-based interactive narrative be used as a constructivist learn-
ing activity? The paper proposes that player agency can be used to
link interactive narrative to learner agency in constructivist theory,
and to classify approaches to interactive narrative. The traditional
question driving research in interactive narrative is, ‘how can an in-
teractive narrative deal with a high degree of player agency, while
maintaining a coherent and well-formed narrative?’ This question
derives from an Aristotelian approach to interactive narrative that,
as the question shows, is inherently antagonistic to player agency.
Within this approach, player agency must be restricted and manip-
ulated to maintain the narrative. Two alternative approaches based
on Brecht’s Epic Theatre and Boal’s Theatre of the Oppressed are
reviewed. If a Boalian approach to interactive narrative is taken the
conflict between narrative and player agency dissolves. The question
that emerges from this approach is quite different from the traditional
question above, and presents a more useful approach to applying in-
teractive narrative as a constructivist learning activity
Psychoanalysis, Nazism and "Jewish science"
No full textIn this paper the author offers a partial examination of the troubled history of psychoanalysis in Germany during the Nazi period. Of particular interest is the impact on psychoanalysis of its 'Jewish origins'--something denigrated by the Nazis but reclaimed by more recent Jewish and other scholars. The author traces the rapid decline of the pre-Nazi psychoanalytic institutions under the sway of a policy of appeasement and collaboration, paying particular attention to the continuation of some forms of psychoanalytic practice within the 'Göring Institute'. He suggests that a feature of this history was the anti-Semitism evidenced by some non-Jewish psychoanalysts, which revealed an antagonism towards their own positioning as followers of the 'Jewish science'
Charisma and Spirituality in the Early Church: A Study of Messalianism and Pseudo-Macarius
No full textThe thesis is an investigation into the concept of Charisma and Spirituality in the Early Church with particular emphasis upon the writings of Ps-Macarius, and of a group of ascetics known as the Messalians, evident in the late fourth / early fifth centuries. The Macarian writings are
examined to see what they reveal about the experiential pneumatic theology of the Early Church, the relationship between Syrian and Hellenic traditions of Christian Rhetoric, and the relationship between Ps-Macarius and the Cappadocian Circle. The Macarian corpus as a whole is examined to assess its rhetorical influences and style. The rhetoric of the Macarian corpus is seen to illustrate a high degree of sophistication. This study also gives definition to two terms that have become imprecise and diverse in their use: 'enkrateia' (self-control), and
`Syrian Christianity'. By isolating the characteristics of enkratefa the definitive stages of an encratic lifestyle are identified. The breaking down of the term into enkrateia, radical enkrateta and exclusive enkrateta enables a much clearer discussion to take place as to the
nature of the encratic theology of a group or individual. The final element of this study is a consideration of the distinct Macarian imagery that is evident within the corpus. Two images are considered in detail, the 'flight of the soul' and 'sober intoxication'. Overall this study
shows the variety of influences upon Ps-Macarius, and the uniqueness of his expression. The influences upon Ps-Macarius include a context of endemic Syrian spirituality, a radical encratic lifestyle, a Hellenic rhetorical training, and a distinct interpretation of Platonic and Neo-
Platonic images, coupled to the wider Judaic / Mesopotamian influences of his Church. It is shown that Ps-Macarius represents an individual voice that is distinct and recognisable amongst the Fathers of the Church
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