Thesis (M. Phil.)--University of Hong Kong, 1993.

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2009 Sep 19

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The soupfin shark, Galeorhinus galeus, is a circum-global shark species of great economical importance. Their reproductive biology is reasonably well understood, but intraspecific differences between global populations necessitate the study o f populations separately. For this study, 70 male and 74 female specimens were collected along the southwestern coast of South Africa between 34°8'S; 18°27'E and 34°24S; 21°25'E. Morphological changes were described and serum steroid hormone concentrations evaluated by enzyme-linked immunosorbent assay (ELISA) over an almost-complete reproductive cycle. Males display an annual spermatogenic cycle that starts with a significant peak in testosterone concentrations coinciding with the start o f spermatogenesis around April-May. Testosterone levels decrease to reach a minimum in late-winter after which spermiogenesis commences. The prevalence of spermiogenic cysts in the testis increase to reach a peak between February and April, after which mating occurs until about July. Females (aplacentally viviparous) are suggested to have a triennial cycle, similar to the Brazilian & Australian populations, but different from the Californian & Mediterranean populations. During the first year after parturition there is not much reproductive development. The following year sees increased vitellogenic activity in ovarian follicles and development of the oviducal glands and uteri. Ovulation then occurs towards the end of that year. Mating is suggested to precede ovulation by two to three months necessitating sperm storage by the females in their oviducal glands. A 12-15 month gestation ensues and ends in parturition the following summer. Testosterone and estradiol levels fluctuate together and are involved in the preparation for ovulation and oviducal gland development. Progesterone levels show two distinct peaks during the year, in both immature and mature females, and could not yet be functionally linked to any reproductive activity or condition. This cycle is not very tightly synchronised among the South African females. / AFRIKAANSE OPSOMMING: Die vaalhaai, Galeorhinus galeus, kom wereld-wyd voor en is van groot ekonomiese belang in baie lande. Die spesie se voorplantings biologie is reeds redelik deeglik ondersoek maar intraspesifieke verskille tussen verskillende wereld populasies noodsaak die bestudering van populasies afsondelik. Daar is 70 mannetjies en 74 wyfies versamel vir hierdie studie langs die Suid Afrikaanse suid-wes kus tussen 34°8'S; 18°27'E and 34°24S; 21°25'E. Morfologiese veranderinge is beskryf en serum hormoon konsentrasies is ge-evalueer deur middel van die ELISA tegniek vir 'n amper-volledige voortplanting siklus. Mannetjies vertoon 'n jaarlikse spermatogeniese siklus met 'n piek in testosteroon konsentrasies aan die begin van spermatogenese in April-Mei. Hiema daal testosteroon vlakke tot minimum vlakke in die laat-winter, waama spermiogenese begin. Die proporsie spermiogeniese siste in die testis vermeerder tot maksimum waardes bereik word tussen Februarie en April. Paring vind hiema plaas tot omtrent Julie. Wyfies (aplasentaal vivipaar) het 'n voorgestelde driejaarlikse siklus, soortgelyk aan die Brasiliaanse & Australiese populasies maar anders as die Kalifomiese & Mediterreense populasies. Tydens die eerste jaar na bevalling vind daar nie veel voortplantings ontwikkeling plaas nie. Die daaropvolgende jaar verhoog vitellogeniese aktiwiteit in die ovarium follikels en ontwikkeling van die dopkliere en uteri. Ovulasie vind nader aan die einde van hierdie jaar plaas. Paring vind heel moontlik twee tot drie maande voor ovulasie plaas, wat noodsaak dat die wyfies sperm moet stoor in hulle dopkliere. 'n 12- 15 maande dratyd begin na ovulasie en eindig in geboorte teen die volgende somer. Testosteroon en estradiol konsentrasies fluktueer saam en speel 'n rol tydens voorbereidings vir ovulasie en dopklier ontwikkeling. Progesteroon vlakke piek twee maal gedurende die jaar, in beide onvolwasse en volwasse wyfies, maar dit kon nog nie funksioneel geassosieer word met enige voortplantings aktiwiteit of toestand nie. Die siklus is nie baie nou gesinkroniseer onder die Suid Afrikaanse wyfies nie.

Blackberries have been enjoyed for their delicious flavor and high nutritional value for hundreds of years. In North America, blackberries were cultivated since 1850-1860. Blackberries have their characteristic and unique aromas depending on the cultivar and growing conditions. The objective of this study was to evaluate the impact of seasonal variation and growing environment on blackberry aroma. Volatile compositions of 'Marion' and 'Thornless Evergreen' blackberries from three growing seasons were analyzed using gas chromatography-flame ionization detection (GC-FED) and GC-mass spectrometry (GC-MS). Seasonal variations were observed for some volatile compounds in these two blackberry cultivars. In 'Marion', the compounds were mainly acids, while in 'Thornless Evergreen', they were mainly acids, alcohols, and a few terpenoids. Although seasonal variations were present, it was generally observed that the most abundant volatiles in 'Marion' blackberry were acetic, 2/3-methylbutanoic, hexanoic and decanoic acids and linalool, whereas the most abundant volatiles in 'Thornless Evergreen' were 2-heptanol, hexanol, octanol, α-pinene, nopol and/p-cymen-8-ol. Compared with 'Marion', 'Thornless Evergreen' contained significantly more total volatiles, especially in alcohols, terpenoids and phenols, whereas 'Marion' contained more organic acids. Odor Activity Values (OAVs) were used to determine the most potent odorants in each cultivar. The compounds with high odor activity values (OAV > 10) in 'Marion' were ethyl hexanoate, β-ionone, linalool, 2-heptanone, 2-undecanone, α-ionone and hexanal. The compounds with high odor activity values (OAV > 10) in 'Thornless Evergreen' were ethyl hexanoate, 2-heptanone, ethyl 2-methylbutanoate, 2-heptanol, 3-methylbutanal, α-pinene, limonene, p-cymene, linalool, t-2-hexenal, myrtenol, hexanal, 2- methylbutanal and sabinene. To investigate the influence of growing environment on blackberry aroma, aroma extraction dilution analysis (AEDA) was employed to characterize the aroma profile of 'Chickasaw' blackberries from two growing regions in United States: Oregon and Arkansas. Eighty-seven odorants were detected in the two berries, in which seventy-seven could be identified. Comparative AEDA analysis showed that the berries grown in these two regions had similar aroma compositions, however, those odorants had various aroma impacts in each region. The compounds with high FD factors in Oregon's 'Chickasaw' were ethyl butanoate, linalool, methional, trans,cis-2,6-nonadienal, cis-l,5-octadien-3-one, and 2,5-dimethyl-4-hydroxy- 3(2H)-furanone, whereas in the 'Chickasaw' grown in Arkansas, they were ethyl butanoate, linalool, methional, ethyl 2-niethylbutanoate, β-damascenone and geraniol. The flavor formation in 'Chickasaw' blackberries was largely influenced by their growing environment. / Graduation date: 2005

Molecular nitrogen is a highly abundant element in the atmosphere; it is stable and not very reactive. Anthropogenic activities have caused greater concentrations of nitrogen-containing compounds that are highly reactive and ultimately toxic. Reactive nitrogen concentrations have become a growing concern on the South African Highveld, with satellite images indicating very high nitrogen dioxide concentrations in the region. This study investigates the nitrogen budget on the Highveld through the analysis of the nitrogen species emitted into the atmosphere on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data was collected at Elandsfontein monitoring site, which is centrally located on the industrialised Highveld. The formation and interaction of nitric oxide (NO), nitrogen dioxide (NO2), and nitrate (NO3) are a major focus in the study. NOx concentrations are higher in winter (6.5 to 8.5 μg.m-3) as a result of stable atmospheric conditions. NO3 concentrations also peak during winter (3.5 to 5.5 μg.m-3), with a distinct biomass burning peak during July and August. Diurnally, NOx concentrations indicate a tall-stack industrial source, with concentrations peaking at midday. NO3 concentrations are higher at night and lower during the day, as during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicate that the conversion rate of NO to NO2 is highly variable as a result of varying atmospheric factors. These rates range from 11% to 59% per hour. Rates of dry deposition of NO, NO2 and NO3 are generally higher during winter as a result of higher concentrations and increased atmospheric stability, which prevents transport out of the region. Nitrogen is predominantly deposited as NO2 throughout the year, except during spring when NO3 deposition dominates. The total amount of nitrogen deposited to the Mpumalanga Highveld region is in the range of 6.7 to 13.1 kg ha-1 yr-1, which is well below the stipulated critical load value. Such deposition therefore does not pose significant threats to the natural environment on the Highveld. Between 4% and 14% of the total emitted nitrogen on the Highveld is deposited to the surface via wet and dry deposition. The remainder stays in the atmosphere and is advected out of the region.

Regions that have experienced recent successive cold winters such as the Northeast of North America and Siberia have endured critical social and economic impacts from anomalous low temperatures in recent years, despite warming global temperatures. It is well known that the Tropospheric Polar Vortex (TPV), or jet stream, is a primary influence on many mid-latitude winter weather patterns. However, the strong circumpolar westerlies that maximize at around 60° latitude just above the tropopause, known as the Stratospheric Polar Vortex (SPV), can affect tropospheric circulation and thus winter weather in the Northern Hemisphere. Strong upward propagating waves can affect the geographic extent and strength of the SPV resulting in a weakened polar vortex state, which can in turn bring persistent weather events to the mid-latitudes. Here, an index of SPV spatiotemporal variability is presented using observation based analysis of zonal wind and geopotential height to show changes in SPV behavior at a seasonal scale from 1950-2018. Utilizing the CMIP5 suite of global climate models, historical and projected simulations of the SPV's climatological extent and strength are analyzed from 1915 to the end of this century, taking into account models with enhanced stratospheric representation. Simulated results are largely consistent with trends in the observational data, which suggest continued increases in average SPV size throughout this century. If future SPV disturbances increase in frequency, there could be negative impacts in ecosystem and agricultural health, infrastructure damage, and to human safety. A more advanced understanding of SPV trends and anomalous events could improve forecasts of cold air outbreaks (CAOs) and severe or persistent winter weather.

This research was conducted in the Mamora cork oak forest of Morocco to: (1) Describe the impacts of sheep grazing (none, 35% use, 70% use) in March, April, May and June of 1987 and 1988 on seasonal forage production; (2) evaluate the effects of these factors on annual changes in herbaceous foliar cover and botanical composition; and (3) determine their effects on seasonal changes in forage quality of the herbaceous vegetation. Neither the month of 1987 nor the degree of use had significant effects on the rate of herbage accumulation. In 1988, the month of grazing, the degree of use and their interaction had significant effects on all rates of herbage accumulation except that between May and June for the March grazed treatment. For the April, May and June treatments, grazing depressed the forage production of the subsequent months. The interaction of the month of grazing and the degree of use had no significant effect on the botanical composition of all groups of species. Averaged over the season, the other forbs were the dominant group of species. Total canopy cover was significantly affected by the year only. The 1988 total vegetative ground cover was significantly higher than the 1987 and 1989 ones as a result of the impacts of the intensity and distribution of rains on vegetative growth, development and distribution. The degree of use had a significant effect on the forage nutrients only for some grazing treatments. It seemed that the effect of the grazing intensity on forage nutrients of the subsequent months is more evident when grazing occurs early in the season. This study developed the first information for this area related to the response of the vegetation to the time and the intensity of grazing. The results suggest that scheduling intensity and timing of grazing livestock might be a key factor in community dynamics. Combined research on grazing management, fertilization and seeding should be undertaken and implemented in the next Mamora management plan. / Graduation date: 1992

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