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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

The Neuroendocrinology of Seasonal Aggression in Female Syrian Hamsters

Gutzler, Stephanie 28 July 2009 (has links)
Aggression is a feature of many clinical disorders including autism, Alzheimer’s disease, bipolar disorder, and schizophrenia. The available treatment options act to prevent impulsive aggression through modulation of GABAergic and dopaminergic pathways which come with metabolic and dyskinetic side effects. The mechanism underlying aggressive motivation, however, has not been elucidated. In addition, previous studies have been heavily biased towards males of various species. Mimicking changes in day length, or photoperiod, in the laboratory is a natural manipulation used to examine seasonal changes in aggressive behavior in many species. In response to the reduction in the duration of light exposure, animals undergo gonadal regression and become reproductively quiescent. During this non-breeding season in male photoperiod-responsive animals, aggressive behavior increases significantly. Although studies have shown offensive aggression remains elevated in female rodents, seasonal regulation of this behavior in females has not been thoroughly studied. The neuropeptide arginine-vasopressin (AVP) has been implicated in the facilitation of aggressive behavior in male rodents and fishes; therefore, it is useful to examine AVP as a modulator of seasonal aggression in females. Because the actions of AVP in female social behavior may be hormonally-dependent, we investigated the hormonal mechanisms that regulate the expression of AVP receptors and the behavioral actions of AVP on aggression. In addition to changes in gonadal steroid hormones during the non-breeding season, we identified photoperiod-dependent alterations in adrenal hormone secretion as AVP plays a role in regulation of hypothalamic-pituitary-adrenal axis (HPA) activity and anxiety-like behaviors in animal models.
122

Farmers' perceptions of the "Unleashing the Power of Cassava in Africa in Response to the Food Crisis" (UPoCA) project : Experiences from Malawi

Vuong, Thao Thi Phuong January 2012 (has links)
The “Unleashing the Power of Cassava in Africa in Response to the Food Price Crisis” (UPoCA) project carried out by the International Institute of Tropical Agriculture from 2008 to 2010 aimed to assist farmers to increase food security and improve livelihoods through promoting cassava cultivation. In this study, 120 beneficiary households of the UPoCA project in Kasungu and Dowa provinces in Malawi were interviewed using a semi-structured questionnaire together with key informant interviews and focus group discussions. The aim was to find out their perceptions of the UPoCA project, food security situation and gendered differences, through which sustainability aspects of the project were discussed. Using the SPSS 19 software, descriptive statistics, chi-square tests and logistic regressions were generated for statistical results. In general, despite issues regarding quality and timeliness of the seed distribution service the majority of the beneficiary households were satisfied with the project stating that it helped improve their food security and livelihoods. However there emerged issues of exclusion of the most vulnerable households and the low participation of female-headed households which were initially targeted by the project. The study also found out the prevalence of seasonal hunger among the studied households and challenges facing the farmers in growing cassava which affect the adoption of the crop and the project’s sustainability. The study suggested that future similar projects should be designed for a longer duration than UPoCA. They should use clear criteria to identify target beneficiaries, exercise thorough monitoring on quality of distributed planting materials and time delivery as well as put more focus on training.
123

Tropical and subtropical estuaries¡¦ CO2 fluxes and mechanisms-Case study of Taiwan

Fu, Yu-Han 28 June 2012 (has links)
Carbon dioxide is the most important greenhouse gas and the major factor leading to the global climate change problem. In previous studies, the ocean is considered to be the major storage of anthropogenic carbon dioxide. However, evaluation of the global CO2 flux seldom includes the estuarine and coastal regions. It should be noted that the current estimate is based on a very limited data set. In particular, data from subtropical and tropical river estuaries are scarce. Many researches point out that the estuary is a CO2 source to the atmosphere, but the data is insufficient so one couldn¡¦t obtain the total CO2 flux accurately. In this study, our team sampled 25 estuaries based on field surveys covering four seasons in Taiwan, aiming to better quantify the estimation of CO2 flux in the coastal regions. The dissociation constants of carbonic acid are unavailable to calculate the fCO2 in the low salinity (S<1). Therefore, the difference (%) between measured and calculated is very large but will be reduced with increasing salinity. Furthermore, in the process of measuring total alkalinity and pH, accuracy may reduce because of humic acid and variations of ionic strength. No matter in the western or eastern estuaries, most of fCO2 values is higher than the atmosphere. And they decrease downstream with increasing salinity. The fCO2 is higher in the west than in the east, because of human activities. Neither group of estuaries shows obvious seasonal variability. The fCO2 in the estuaries has a relationship with salinity, because of mixing with sea water. Because fCO2 is controlled by biological activity, it also has a relationship with AOU, pH and nutrients (NO3- and PO43-). In the east, the fCO2 has no correlation with many parameters. It is probably that the slope is steeper and the river length is shorter in the east than in the west resulting in short resident time. So that many reactions are not complete before the water exports to the sea. The average water-to-air CO2 flux is 24.6¡Ó19.2 (mol C m-2 y-1), which is 3.5 times the value of Pearl River (6.9 mol C m-2 y-1) but similar to the world average (23.7¡Ó33.1 mol C m-2 y-1). The CO2 flux is the highest in spring (81.7¡Ó15.8 mmol C m-2 d-1) and the lowest in winter (54.1¡Ó132 mmol C m-2 d-1). Upper/mid/lower estuaries are operationally defined as those areas of estuaries with salinities below 2, between 2 and 25, and above 25, respectively. The trends of fCO2 have good relationships with AOU and PO43- in the upper estuaries. The reason is probably caused by human activities and biological respiration. The phenomenon is more complex in the mid than in the upper estuaries. Consequently, the fCO2 has a good correlation with pH and DIC in the mid estuaries as a result of organic matter decomposition. However, in the lower estuaries, the variation of fCO2 is subjected to biological respiration and mixing with sea water. The fCO2 is the highest in the upper estuaries (2228¡Ó92.0 uatm)¡Athe average water-air CO2 flux is 42.3¡Ó1.54 (mol C m-2 y-1). Measured fCO2 in the mid estuaries is 1302¡Ó353 (uatm) and the average CO2 flux is 25.8¡Ó1.26 (mol C m-2 y-1). The lowest fCO2 (559¡Ó14.9 uatm) is found in the lower estuaries and the CO2 flux is 7.38¡Ó7.45 (mol C m-2 y-1). The 106 estuaries of the globe are divided into three parts by salinity. The fCO2 is 3033¡Ó1078, 2277¡Ó626 and 692¡Ó178 uatm in the upper, mid and lower estuaries, respectively. The average CO2 flux is 68.5¡Ó25.6¡B37.4¡Ó16.5 and 9.92¡Ó15.2 mol C m-2 y-1, respectively. Geographically estuaries in all three latitude bands (¡Õ23.5o, 23.5-50o and ¡Ö50o) are generally sources of CO2. Interestingly, water-to-air fluxes do not significantly, and all fall around 24 mol C m-2 y-1 although the flux is slightly lower at high latitude. The water in estuaries release CO2 in all seasons although the flux seems to be highest in autumn (73.2¡Ó 93.4 mmol C m-2 d-1) and lowest (53.4¡Ó65.1 mmol C m-2 d-1) in winter. The average CO2 flux is 23.9¡Ó33.1 mol C m-2 y-1, and the total CO2 flux is 0.26 Pg C y-1. Next, we estimate the tropical rivers¡¦ carbon fluxes using carbon parameters concerning 175 rivers globally between 30oN and 30oS. The specific DIC yield (flux/area) are 0.63, 3.33, 9.79 and 3.38 g C m-2 y-1 in tropical Africa, the Americas, Asia and Oceania, respectively. The DIC flux in Asia is the highest among the four regions, mainly because the percentage of carbonate rock is highest there and the second highest water discharge there. The PIC fluxes are 7.40¡Ñ1012 g C y-1 in Africa, 2.82¡Ñ1013 g C y-1 in the Americas, 1.53¡Ñ1013 g C y-1 in Asia and 2.49¡Ñ1011 g C y-1 in Oceania. The DOC fluxes are 2.80¡Ñ1013, 5.82¡Ñ1013, 4.50¡Ñ1013 and 4.48¡Ñ1012 g C y-1 in tropical Africa, the Americas, Asia and Oceania, respectively, for a total DOC flux of 0.136 Pg C y-1. Tropical rivers provide 0.53 Pg C y-1 of carbon to the oceans, of which 39.8¢H is DIC, 25.7¢H is DOC, 9.7¢H is PIC and 24.8¢H is POC.
124

Distributions and variations of dissolved organic carbon in the Taiwan Strait and Taiwanese rivers

Pan, Pei-Yi 04 July 2012 (has links)
Dissolved organic carbon (DOC) is one of the largest pools of carbon in the ocean, and is of the same size as the carbon dioxide in the atmosphere. Estuaries connecting the land and the ocean are one of the most important DOC sources to the ocean, and play an important role in the global carbon cycle. Because of their complex chemical, physical, geological and biological properties, estuaries have become rich ecological environment. In this study, we investigated the seasonal distributions of DOC in the Taiwan Strait (TS) and Taiwanese rivers, aiming to understand the distributions and variations of DOC in different seasons. The results show that DOC concentrations are generally the highest in the upper estuary, and then decrease downstream due to mixing with the low DOC seawater. The process of river flow constantly accumulates terrestrial material, and the DOC shows positive correlations with Chl. a, CH4 and BOD (Biochemical Oxygen Demand), suggesting that biological activities and pollutions could be sources of DOC in the estuary. The DOC concentrations (salinity<1) varied in dry (Nov.-Apr.) and wet (May-Oct.) seasons with ranges of 42-1185 £gM (mean=245¡Ó254£gM; n=32) and 18-565 £gM (mean=183¡Ó151£gM; n=24), respectively. The total DOC flux of 25 rivers is 87.8 Gg C/yr, which can be translated to the fluxes of all rivers in Taiwan to be 101.9 Gg C/yr. The amount of DOC flux in Taiwan is only about 0.07% of the tropical area, but the per unit area flux (3.92 gC /m2 /yr) is almost twice those of the tropical rivers (2.13 gC /m2 /yr). In Taiwan, the population density and land use are higher than the world average. Consequently, the impacts of the environment by human activities reveal the utmost export of DOC, and need further investigation. Next, in the TS, the DOC shows significant negative correlations with Sigma-T, and the distributions of DOC are mainly controlled by physical mixing in both winter and summer. In the western TS, DOC concentration is relatively high, compared to the eastern part, and is because of low temperature and salinity, but high DOC coastal China current flowing from north to south. DOC concentration decreases with increasing depth owing to the intrusion at depth by the Kuroshio, which contains relatively low DOC. In winter, the import of coastal China current brings more nutrients from north to south, and supports the growth of bacteria which depletes the DOC and oxygen. As the result, DOC decomposition rate is higher in winter than in summer. The TS¡¦s DOC fluxes in summer (northern TS: 3.85¡Ñ1012mol C/yr¡Fsouthern TS: 3.75¡Ñ1012mol C/yr) are higher than in winter (northern TS: 3.69¡Ñ1012mol C/yr¡Fsouthern TS: 2.84¡Ñ1012mol C/yr). Main differences are due to the prevailing southwest monsoon winds in summer transporting more water from the South China Sea to the TS, and the river discharge brings more terrigenous organic matters into the TS. Therefore, the DOC export in summer is higher than in winter.
125

Seasonal and Regional Variability of Stratospheric Dehydration

Christenberry, Aaron Joseph 2012 May 1900 (has links)
We analyze output from a domain-filling forward trajectory model in order to better understand the annual cycle of water vapor entering the stratosphere. To do this, we determine the minimum water vapor saturation mixing ratio along each trajectory (the final dehydration point or FDP) and assume that the parcel carries that much water vapor into the stratosphere. In the annual average, the tropical Western Pacific, equatorial Africa and South America, and Southeast Asia are found to be the locations of the most frequent FDPs. Looking at individual seasons, we find that FDPs in the tropical western Pacific tend to occur in the summer hemisphere, with FDPs over South America and Africa occurring predominantly during the boreal winter. During boreal summer, a dehydration maximum occurs in the Asian monsoon region. In the annual average, FDP maxima occur at 99 and 84 hPa. Looking at individual seasons, we find that FDPs occur at higher altitudes (centered at 84 hPa) during boreal winter and at lower altitudes (99 hPa) during boreal summer. The annual cycle in FDP altitude combines with the annual cycle in tropical tropopause layer temperatures to generate the observed annual variations in water vapor entering the stratosphere.
126

Host-specificity and seasonal variation of dicyemid mesozoan infection in octopuses of the tropical waters

Hsu, Chia-Ling 02 September 2003 (has links)
Dicyemid mesozoans are endoparasites inhabited in benthic cephalopod molluscs. Previous studies of dicyemids were mostly concentrated on their taxonomy. The life cycle remains a mystery since Cavolini observed this animal in 1787. The purpose of this study is to investigate further on the dicyemid life cycle building on the limited knowledge from previous studies, and investigate the infection of dicyemid in octopuses in tropical waters, using the area in the southwestern Taiwan as a model. A total of 324 octopus hosts was collected¡Aincluding 3 genera and 13 species from DungGang Fish Market from 2001 to 2002. There were 9 host species detected with dicyemid mesozoans including 14 species within 2 genera. Moreover, there is no dicyemid species overlap among the octopus species indicating high host-specificity. There is large range of the dicyemid infection prevalence among octopod hosts. Cistopis indicus has the highest prevalence (91%) and Octopus luteus the lowest (20%) in this study. In C. indicus, the infected mechanism correlated with season. The infusoriform larvae of dicyemid mesozoan dispersal from the host to sea water in the autumn and winter, then entering host in the spring and summer. The change of dicyemid life cycle stage in the C. indicus kidney correlates with the sharp decrease of infection intensity. However, the dicyemid infection in Octopus marginatus correlates with body size, not with season. Besides, there is significant difference of dicyemid development between two kidneys of the same individual, both in the analysis of C. indicus and O. marginatus. It indicates the separated way of dicyemid infection into two sides of kidneys.
127

The Analysis of the Causes and the Variations on Ozone and Related Air Pollutants in Taitung Area

Kuo, Chien-cheng 06 September 2006 (has links)
ABSTRACT Taitung area was commonly seen as a particularly clean environment. But the air quality has diminished lately similar to that seen in some parts of the populated western area in Taiwan, with ozone (O3) concentration levels rising every year. Because ozone is a byproduct of photochemistry, its accumulation is not only related to the discharge of local pollutants such as nitrogen oxide compounds (NOx), volatile organic compounds (VOC) and the introduction of external pollutants, but also related to the meteorological conditions. This research began with comparing the long-term trends of ozone concentration level and related pollutants in the Taitung area with those found in other survey stations spread in Taiwan. Through factor analysis, the relationship between air pollutants and meteorological parameters are analyzed. Finally, a screening of the events of abnormal ozone concentrations, followed with detailed analysis of the hourly data during these events and the discussion of the possible reasons for the comparatively poor air quality during these events and their correlations with seasons and meteorological conditions. Analysis of the trends in monthly averaged concentration of ozone shows that the annual rate of change (AR) is increasing at all stations under this study, except the Guanyin station being -0.18%. Taitung station has relatively higher levels every spring (March - May) and fall (October ¡V November); the annual rate of change is higher than other east area in Taiwan and the Hengchun station. These seasonal variation (SV) shows a progressively increasing north to south trend, Hengchun station being the highest and Taitung station being the second highest, indicates that concentrations of ozone are influenced by seasonal changes. By using the method of factor analysis to analyze the relation among ozone concentrations, meteorological parameters and pollution parameters, resulted in a direct relationship to the wind speeds over the four seasons. The results show a negative relationship to the atmospheric pressure during summer. The ozone concentrations of the Taitung station show a direct relationship to the Hualian station, which indicates the north to south dispersion relationship. The Analysis of the abnormal event also shows that typhoons may be an important carrier for transporting external pollutants into the area.
128

Investigation of temporal and spatial characteristics of carbonyl compounds in the Atmosphere in Kaohsiung

Wu, Chun-I 29 June 2007 (has links)
The concentrations of atmospheric carbonyls were studied by the LpDNPH-Cartridge and the microcomputer air sampling device at Nanzi and Siaogang sites in Kaohsiung city. Source apportionment was determined by the factor analysis. The results showed that the highest concentrations of carbonyls was acetaldehyde (27.83 £gg/m3) at Nanzi, followed by formaldehyde (5.03 £gg/m3). At Siaogang, the highest concentrations of carbonyls was acetaldehyde (28.91 £gg/m3), followed by formaldehyde (6.92 £gg/m3). The concentrations of total carbonyls was higher at Siaogang (57.86 £gg/m3) than those at Nanzi (49.74 £gg/m3) . The concentrations of total carbonyls at Nanzi were 65.42 £gg/m3 in summer and 25.06 £gg/m3 in winter, and were 85.09 £gg/m3 in summer and 37.12 £gg/m3 in winter at Siaogang, due to the fact that summer has stronger photochemical activities than in winter. Additionally, peak rush hours of the traffics, either in the morning or at night, would result in increased concentration of Carbonyls was higher. The concentrations of atmospheric carbonyls were studied by the LpDNPH-Cartridge and the microcomputer air sampling device at Nanzi and Siaogang sites in Kaohsiung city. Source apportionment was determined by the factor analysis. The results showed that the highest concentrations of carbonyls was acetaldehyde (27.83 £gg/m3) at Nanzi, followed by formaldehyde (5.03 £gg/m3). At Siaogang, the highest concentrations of carbonyls was acetaldehyde (28.91 £gg/m3), followed by formaldehyde (6.92 £gg/m3). The concentrations of total carbonyls was higher at Siaogang (57.86 £gg/m3) than those at Nanzi (49.74 £gg/m3) . The concentrations of total carbonyls at Nanzi were 65.42 £gg/m3 in summer and 25.06 £gg/m3 in winter, and were 85.09 £gg/m3 in summer and 37.12 £gg/m3 in winter at Siaogang, due to the fact that summer has stronger photochemical activities than in winter. Additionally, peak rush hours of the traffics, either in the morning or at night, would result in increased concentration of Carbonyls was higher. Source apportionment analysis using factor analysis shows that the principle sources at Nanzi were traffic exhausts (motor, diesel, and gasoline vehicle) and stationary sources (industry, restaurant and chemical processes). The main sources at Siaogang were traffic exhausts (motor and gasoline vehicle), stationary sources (industry and restaurant) and secondary photo-chemical reactions.
129

Seasonal Variation of Chemical Hydrography in the Southern Penghu Channel

Lin, Hsin-chi 26 June 2003 (has links)
Abstract The Penghu Channel (PHC), situated in the southeastern Taiwan Strait (TS), is the major conduit for the South China Sea water (SCSW) and Kuroshio subsurface water flowing into the TS. However, the previous studies in this area were largely focused on the aspects of physical oceanography, with scant attention to the chemical hydrography is poorly studied, and therefore little understood. In order to better understand the seasonal variations of chemical hydrography in the southern PHC, we conducted a systematic survey of chemical hydrography aboard R/V Ocean Research III during cruises in January, March, July and October 2001 as well as March 2002. The water above 200m in the southern PHC is characteristic of salinity and temperature between those of SCSW and Kuroshio water (KW), suggesting it is mixing between these two waters. Nonetheless, the salinity and temperature below 200m are dominated by the SCSW. The relative amount of SCSW and KW flowing into the PHC has varied seasonally and annually. During the transition period of monsoon, KW was more than SCSW, but SCSW had a larger quantity during the northeast and southwest monsoon. The slope of the regression line between the d13CDIC and PO4-3 (0-100m, -0.55; below 100m, -0.30) indicates that the distributions of d13CDIC and PO4-3 in the study area may be controlled by the effect of air-sea exchange or the mixing of different water masses or both. In addition, to evaluate the overall error in d13CDIC analysis, we have checked carefully whether the different storage bottles, the various duration of storage, and different amount of saturated HgCl2 solution added in the water samples would produce uncertainty on the d13CDIC analysis. Our results show no significant discrepancy among these the different treatments, suggesting that the water samples can be stored without measurable d13CDIC change at least for 3 months.
130

Survival, seasonal movements, and cover use by lesser prairie chickens in the Texas Panhandle

Toole, Benjamin Edwin 01 November 2005 (has links)
Lesser prairie chicken (Tympanuchus pallidicinctus; LPC) numbers have declined considerably in Texas since the early 1900s. As with other prairie chicken species, reasons for declining ranges and numbers have been attributed primarily to degradation and fragmentation of habitats. Until my study, no telemetry-based research on LPC has been conducted in the Rolling Plains of the Texas Panhandle. I radio-tagged and monitored LPCs in 2001 (spring??winter) and 2002 (spring) at a stable population in a native rangeland landscape (Study Area I) and in a declining population in a fragmented rangeland and agricultural landscape (Study Area II). No significant (P < 0.05) differences in survival were detected for combined study areas between years, or between study areas within years. Ranges and movements, as independent criteria by season, sex, and age classes combined were similar (P > 0.05) for both study areas. Lesser prairie chickens predominately occupied native rangeland cover types (>85%) compared to non-native rangelands at both study areas. Total invertebrate dry mass for all orders differed between native rangeland and Conservation Reserve Program (CRP) sites at Study Area II. Over 32 times more dry mass of invertebrates was collected at the native rangeland site than were collected at the CRP site. Herbaceous cover differed significantly for grasses (P < 0.01), forbs (P < 0.01), and bare ground (P < 0.01), but not for litter (P = 0.43) or woody cover (P = 0.63) between study areas. The similar range sizes, movement distances, and cover use observed for both study areas may provide insight into minimum area requirements for LPCs within the Rolling Plains in the Texas Panhandle.

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