AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having prim...AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having primary open angle glaucoma(POAG).METHODS:Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential(PRVEP)were assessed in 100 patients with POAG.The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated(full field)and displayed on VEP monitor(colour 14')by an electronic pattern regenerator inbuilt in an evoked potential recorder(RMS EMG EP MARK II).RESULTS:The results of our study indicate that there is a highly significant(P【0.001)negative correlation of P100 amplitude and a statistically significant(P【0.05)positive correlation of N70 latency,P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student’s t-test.CONCLUSION:Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values.Conversely,as PSD increases the magnitude of VEP excursions were found to be diminished.展开更多
This study focused on identifying drought patterns particularly during the growing seasons along the coastal zone of Tanzania in order to facilitate the determination of drought impacts on forest Ecosystem. The growin...This study focused on identifying drought patterns particularly during the growing seasons along the coastal zone of Tanzania in order to facilitate the determination of drought impacts on forest Ecosystem. The growing seasons were March, April and May (MAM) referred as long growing season and October, November and December (OND) which is known as short growing season. The main data were precipitation from 16 weather stations covering the coastal zones of Tanzania. Standardized Precipitation Index (SPI) was used to establish meteorological drought patterns. The duration of records was between 34 and 59 years depending on the available data on the concerned stations. The SPI time series of 3 and 12 months showed that the coastal region of Tanzania experienced frequent drought conditions ranging from mild, moderate, severe and extreme droughts during both short and long growing seasons. It was found that the coastal zone of Tanzania experienced higher drought duration, severity and intensity with frequent extreme events after 2000 than before. Despite that Kisarawe area revealed low frequency of drought events (88%) than other study areas;it exhibited greater frequency of extreme droughts (46%) over the whole study areas. Higher drought duration (40 months) and severity (sum of SPI -36) were observed for precipitation data from Unguja Islands, while data from Julius Nyerere International Airport areas displayed higher drought intensity (SPI value of -1.9). Generally, Tanzania coastal zone was never completely without drought or anomalously wet conditions at any time scale during the period of record. The coastal zone was nearly entirely in drought periods especially the last decade after 2000. This suggests that vegetation in the coastal zone might have experienced the impacts of these droughts within the period. The magnitude of the impacts will be understood by tracking changes of biomass and forest cover along the coastal zone within the last decade from 2000 to 2011 in addition to the 1990/92 which experienced drought dominance for Pemba.展开更多
Drought acutely affects economic sectors, natural habitats and communities. Understanding the past spatial and temporal patterns of drought is crucial because it facilitates the forecasting of future drought occurrenc...Drought acutely affects economic sectors, natural habitats and communities. Understanding the past spatial and temporal patterns of drought is crucial because it facilitates the forecasting of future drought occurrences and informs decision-making processes for possible adaptive measures. This is especially important in view of a changing climate. This study employed the World Meteorological Organization(WMO)-recommended standardized precipitation index(SPI) to investigate the spatial and temporal patterns of drought in Zambia from 1960 to 2016. The relationship between the occurrence of consecutive dry days(CDD; consecutive days with less than 1 mm of precipitation) and SPI was also investigated. Horizontal wind vectors at 850 hPa during the core of the rainy season(December–February)were examined to ascertain the patterns of flow during years of extreme and severe drought; and these were contrasted with the patterns of flow in 2007, which was a generally wet year. Pressure vertical velocity was also investigated. Based on the gamma distribution, SPI successfully categorized extremely dry(with a SPI value less than or equal to –2.0) years over Zambia as 1992 and 2015, a severely dry(–1.9 to –1.5) year as 1995, moderately dry(–1.4 to –1.0) years as 1972, 1980, 1987, 1999 and 2005, and 26 near normal years(–0.9 to 0.9). The occurrence of CDD was found to be strongly negatively correlated with SPI with a coefficient of –0.6. Further results suggest that, during wet years, Zambia is influenced by a clockwise circulating low-pressure zone over the south-eastern Angola, a second such zone over the northern and eastern parts, and a third over the Indian Ocean. In stark contrast, years of drought were characterized by an anti-clockwise circulating high-pressure zone over the south-western parts of Zambia,constraining precipitation activities over the country. Further, wet years were characterized by negative pressure vertical velocity anomalies, signifying ascending motion; while drought years were dominated by positive anomalies, signifying descending motion, which suppresses precipitation. These patterns can be used to forecast drought over Zambia and aid in strategic planning to limit the potential damage of drought.展开更多
In accordance with classificationmethods based on either product standards orproperty standards,this paper first groups currentChinese wood-based panel standards into classes.Then,the authors examine and analyze the a...In accordance with classificationmethods based on either product standards orproperty standards,this paper first groups currentChinese wood-based panel standards into classes.Then,the authors examine and analyze the agepattern and adoption scope of these standards,inthe hope such an attempt will promote the construc-tion of a standards system in China.展开更多
文摘AIM:To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation(PSD)of Humphrey visual field could be associated with visual evoked potential(VEP)parameters of patients having primary open angle glaucoma(POAG).METHODS:Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential(PRVEP)were assessed in 100 patients with POAG.The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated(full field)and displayed on VEP monitor(colour 14')by an electronic pattern regenerator inbuilt in an evoked potential recorder(RMS EMG EP MARK II).RESULTS:The results of our study indicate that there is a highly significant(P【0.001)negative correlation of P100 amplitude and a statistically significant(P【0.05)positive correlation of N70 latency,P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student’s t-test.CONCLUSION:Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values.Conversely,as PSD increases the magnitude of VEP excursions were found to be diminished.
文摘This study focused on identifying drought patterns particularly during the growing seasons along the coastal zone of Tanzania in order to facilitate the determination of drought impacts on forest Ecosystem. The growing seasons were March, April and May (MAM) referred as long growing season and October, November and December (OND) which is known as short growing season. The main data were precipitation from 16 weather stations covering the coastal zones of Tanzania. Standardized Precipitation Index (SPI) was used to establish meteorological drought patterns. The duration of records was between 34 and 59 years depending on the available data on the concerned stations. The SPI time series of 3 and 12 months showed that the coastal region of Tanzania experienced frequent drought conditions ranging from mild, moderate, severe and extreme droughts during both short and long growing seasons. It was found that the coastal zone of Tanzania experienced higher drought duration, severity and intensity with frequent extreme events after 2000 than before. Despite that Kisarawe area revealed low frequency of drought events (88%) than other study areas;it exhibited greater frequency of extreme droughts (46%) over the whole study areas. Higher drought duration (40 months) and severity (sum of SPI -36) were observed for precipitation data from Unguja Islands, while data from Julius Nyerere International Airport areas displayed higher drought intensity (SPI value of -1.9). Generally, Tanzania coastal zone was never completely without drought or anomalously wet conditions at any time scale during the period of record. The coastal zone was nearly entirely in drought periods especially the last decade after 2000. This suggests that vegetation in the coastal zone might have experienced the impacts of these droughts within the period. The magnitude of the impacts will be understood by tracking changes of biomass and forest cover along the coastal zone within the last decade from 2000 to 2011 in addition to the 1990/92 which experienced drought dominance for Pemba.
基金on a PhD scholarship sponsored by the University of Edinburgh
文摘Drought acutely affects economic sectors, natural habitats and communities. Understanding the past spatial and temporal patterns of drought is crucial because it facilitates the forecasting of future drought occurrences and informs decision-making processes for possible adaptive measures. This is especially important in view of a changing climate. This study employed the World Meteorological Organization(WMO)-recommended standardized precipitation index(SPI) to investigate the spatial and temporal patterns of drought in Zambia from 1960 to 2016. The relationship between the occurrence of consecutive dry days(CDD; consecutive days with less than 1 mm of precipitation) and SPI was also investigated. Horizontal wind vectors at 850 hPa during the core of the rainy season(December–February)were examined to ascertain the patterns of flow during years of extreme and severe drought; and these were contrasted with the patterns of flow in 2007, which was a generally wet year. Pressure vertical velocity was also investigated. Based on the gamma distribution, SPI successfully categorized extremely dry(with a SPI value less than or equal to –2.0) years over Zambia as 1992 and 2015, a severely dry(–1.9 to –1.5) year as 1995, moderately dry(–1.4 to –1.0) years as 1972, 1980, 1987, 1999 and 2005, and 26 near normal years(–0.9 to 0.9). The occurrence of CDD was found to be strongly negatively correlated with SPI with a coefficient of –0.6. Further results suggest that, during wet years, Zambia is influenced by a clockwise circulating low-pressure zone over the south-eastern Angola, a second such zone over the northern and eastern parts, and a third over the Indian Ocean. In stark contrast, years of drought were characterized by an anti-clockwise circulating high-pressure zone over the south-western parts of Zambia,constraining precipitation activities over the country. Further, wet years were characterized by negative pressure vertical velocity anomalies, signifying ascending motion; while drought years were dominated by positive anomalies, signifying descending motion, which suppresses precipitation. These patterns can be used to forecast drought over Zambia and aid in strategic planning to limit the potential damage of drought.
基金Constructing Technical Standard System for Wood Industry,a national Science Project for technical bases
文摘In accordance with classificationmethods based on either product standards orproperty standards,this paper first groups currentChinese wood-based panel standards into classes.Then,the authors examine and analyze the agepattern and adoption scope of these standards,inthe hope such an attempt will promote the construc-tion of a standards system in China.
