Knowledge of the wind speed distribution is an important information needed in evaluation of wind... more Knowledge of the wind speed distribution is an important information needed in evaluation of wind power potential. Several statistical distributions have been used to study wind data. The Weibull distribution is the most popular due to its ability to fit most accurately the variety of wind speed data measured at different geographical locations throughout the world. Recently, maximum entropy (MaxEnt) distributions based on the maximum entropy method have been widely used to determine wind speed distribution. Li and Li used the MaxEnt distribution for the first time in the wind energy field and proposed a theoretical approach to determine the distribution of wind speed data analytically. Ramirez and Carta discussed the use of wind probability distributions derived from the maximum entropy principle in the analysis of wind energy. In this study, MinMaxEnt distributions defined on the basis of the MaxEnt method are introduced and applied to find wind distribution and wind power density. A comparison of the MinMaxEnt and Weibull distributions on wind speed data taken from different sources and measured in various regions is conducted. The wind power densities of the considered regions obtained from the Weibull and MinMaxEnt distributions are also compared. The results indicate that the MinMaxEnt distributions obtained show better results than the known Weibull distribution for wind speed distributions and wind power density. Therefore, MinMaxEnt distributions can be used to estimate wind distributions and wind power potential.
Pancreatitis is the most serious complication of endoscopic retrograde cholangiopancreatography (... more Pancreatitis is the most serious complication of endoscopic retrograde cholangiopancreatography (ERCP), occurring in 2-20% of the patients. Currently there is no information about the impact of preoperative pancreatitis on the surgical management of periampullary tumors. Ten patients with periampullary tumors and preoperative acute pancreatitis were retrospectively analyzed. Four patients who underwent pylorus-preserving pancreaticoduodenectomy (group A) and 6 patients who underwent total pancreatectomy (group B) were compared with a matching control group (age, gender, stage, tumor and operation type) of 30 patients without pancreatitis (group C) who underwent an operation during the same period. Parameters analyzed were C-reactive protein (CRP), leukocytes, aminotransferases, amylase, lipase, operative time, blood loss, hospital stay, morbidity, and mortality. In the study group, 5 patients had pancreatic adenocarcinoma, 3 had distal bile duct cancers, and 2 had ampullary tumors. None of the patients had severe acute necrotizing pancreatitis that necessitated intervention prior to tumor resection. Preoperative median CRP levels in group B were 8.4- and 5.6-fold higher than those of groups A and C, respectively. In contrast, leukocytes, aminotransferases, amylase, and lipase levels were not significantly different. The presence of acute pancreatitis slightly prolonged the duration of the operation (+15 min), increased morbidity (60 vs. 33%) and lengthened median hospital stay (19.5 vs. 14.5 days) in groups A and B vs. group C. All patients with preoperative pancreatitis were managed without mortality. Preoperative pancreatitis is more commonly seen in patients with non-pancreatic periampullary tumors, and considerably influences surgical management. High preoperative CRP levels indicate a more severe form of pancreatic damage that may necessitate a total pancreatectomy.
Satellite radar altimetry has the ability to monitor variations in surface water height (stage) f... more Satellite radar altimetry has the ability to monitor variations in surface water height (stage) for large wetlands, rivers, and associated floodplains. A clear advantage is the provision of data where traditional gauges are absent. As part of an international program, a complete altimetric analysis of the Amazon Basin is being undertaken. Here, an updated and more rigorous evaluation of the TOPEX/POSEIDON (T/P) data set is presented for the first ˜7.5 years of the mission. With an initial study group of 230 targets, height variability at many ungauged locations can be observed for 30-50%, the range reflecting the clarity of the variations in lieu of instrument limitations. An assessment of the instrument performance confirms that the minimum river width attainable is ˜1 km in the presence of some inundated floodplain. This constraint does allow observation of the main stem (Solimões/Amazon) and the larger tributaries, but rugged terrain in the vicinity of the target additionally places severe limitations on data retrieval. First-order validation exercises with the deduced 1992-1999 time series of stage fluctuations reveal accuracies ranging from tens of centimeters to several meters (mean ˜1.1 m rms). Altimetric water levels in the Solimões and Amazon are particularly well defined with amplitudes <13 m and variations in peak-level timing from May to July. The water-surface gradient of the main stem is found to vary both spatially and temporally, with values ranging from 1.5 cm/km downstream to 4.0 cm/km for more upstream reaches. In agreement with ground-based estimates, the seasonal variability of the gradients reveals that the hysteresis characteristic of the flood wave varies along the main stem and the derived altimetric velocity of this flood wave is estimated to be ˜0.35 m/s. Overall, the altimetric results demonstrate that the T/P mission is successfully monitoring the transient flood waves of this continental-scale river basin.
... to be freshly formed and are too small to be significantly af-fected by riming and aerosolsca... more ... to be freshly formed and are too small to be significantly af-fected by riming and aerosolscavenging processes. ... are detected and opti-cally sized using the transit time between two continuous 532nm frequency-doubled neodymium-doped yttrium alu-minum garnet (Nd:YAG ...
Availability and utilization of computed tomography angiography has been increasing recently. We ... more Availability and utilization of computed tomography angiography has been increasing recently. We aimed to assess the effectiveness of low amount of contrast media and low kV value in order to reduce possible side effects of contrast media and to provide optimization of kV value in the evaluation of the carotid artery with multi-detector computed tomography angiography. Forty one patients were randomized into two groups. Contrast media was administered at a dose of 1 ml/kg in group A patients and of 0.5 ml/kg in group B patients. kV value of 120 in group A and 100 in group B were chosen. Bolus tracking technique was used. Attenuation values of certain arterial segments were measured, and values over 200 HU were considered as significant. North American Symptomatic Carotid Endartherectomy Trial criteria were utilized in the evaluation of stenosis. Image quality in arterial segments of all cases was found to be sufficient for diagnosis. Arterial attenuation values were found to be higher in group B than group A. When compared separately in all arterial segments, there was no statistically significant difference between the groups. For stenosis, 615 arterial segments were evaluated. Moderate stenosis in eight segments and severe stenosis in three segments were identified in group A. Occlusion in three segments, severe stenosis in three segments, and moderate stenosis in 25 segments were detected in group B. Better image quality can be obtained, and the amount of contrast media can be reduced using low kV technique in carotid artery multi-detector computed tomography angiography examination.
Letters to the Editor are welcomed. They may report new clinical or laboratory observations and n... more Letters to the Editor are welcomed. They may report new clinical or laboratory observations and new developments in medical care or may contain comments on recent contents of the Journal. They will be published, if found suitable, as space permits. Like other material ...
Knowledge of the wind speed distribution is an important information needed in evaluation of wind... more Knowledge of the wind speed distribution is an important information needed in evaluation of wind power potential. Several statistical distributions have been used to study wind data. The Weibull distribution is the most popular due to its ability to fit most accurately the variety of wind speed data measured at different geographical locations throughout the world. Recently, maximum entropy (MaxEnt) distributions based on the maximum entropy method have been widely used to determine wind speed distribution. Li and Li used the MaxEnt distribution for the first time in the wind energy field and proposed a theoretical approach to determine the distribution of wind speed data analytically. Ramirez and Carta discussed the use of wind probability distributions derived from the maximum entropy principle in the analysis of wind energy. In this study, MinMaxEnt distributions defined on the basis of the MaxEnt method are introduced and applied to find wind distribution and wind power density. A comparison of the MinMaxEnt and Weibull distributions on wind speed data taken from different sources and measured in various regions is conducted. The wind power densities of the considered regions obtained from the Weibull and MinMaxEnt distributions are also compared. The results indicate that the MinMaxEnt distributions obtained show better results than the known Weibull distribution for wind speed distributions and wind power density. Therefore, MinMaxEnt distributions can be used to estimate wind distributions and wind power potential.
Pancreatitis is the most serious complication of endoscopic retrograde cholangiopancreatography (... more Pancreatitis is the most serious complication of endoscopic retrograde cholangiopancreatography (ERCP), occurring in 2-20% of the patients. Currently there is no information about the impact of preoperative pancreatitis on the surgical management of periampullary tumors. Ten patients with periampullary tumors and preoperative acute pancreatitis were retrospectively analyzed. Four patients who underwent pylorus-preserving pancreaticoduodenectomy (group A) and 6 patients who underwent total pancreatectomy (group B) were compared with a matching control group (age, gender, stage, tumor and operation type) of 30 patients without pancreatitis (group C) who underwent an operation during the same period. Parameters analyzed were C-reactive protein (CRP), leukocytes, aminotransferases, amylase, lipase, operative time, blood loss, hospital stay, morbidity, and mortality. In the study group, 5 patients had pancreatic adenocarcinoma, 3 had distal bile duct cancers, and 2 had ampullary tumors. None of the patients had severe acute necrotizing pancreatitis that necessitated intervention prior to tumor resection. Preoperative median CRP levels in group B were 8.4- and 5.6-fold higher than those of groups A and C, respectively. In contrast, leukocytes, aminotransferases, amylase, and lipase levels were not significantly different. The presence of acute pancreatitis slightly prolonged the duration of the operation (+15 min), increased morbidity (60 vs. 33%) and lengthened median hospital stay (19.5 vs. 14.5 days) in groups A and B vs. group C. All patients with preoperative pancreatitis were managed without mortality. Preoperative pancreatitis is more commonly seen in patients with non-pancreatic periampullary tumors, and considerably influences surgical management. High preoperative CRP levels indicate a more severe form of pancreatic damage that may necessitate a total pancreatectomy.
Satellite radar altimetry has the ability to monitor variations in surface water height (stage) f... more Satellite radar altimetry has the ability to monitor variations in surface water height (stage) for large wetlands, rivers, and associated floodplains. A clear advantage is the provision of data where traditional gauges are absent. As part of an international program, a complete altimetric analysis of the Amazon Basin is being undertaken. Here, an updated and more rigorous evaluation of the TOPEX/POSEIDON (T/P) data set is presented for the first ˜7.5 years of the mission. With an initial study group of 230 targets, height variability at many ungauged locations can be observed for 30-50%, the range reflecting the clarity of the variations in lieu of instrument limitations. An assessment of the instrument performance confirms that the minimum river width attainable is ˜1 km in the presence of some inundated floodplain. This constraint does allow observation of the main stem (Solimões/Amazon) and the larger tributaries, but rugged terrain in the vicinity of the target additionally places severe limitations on data retrieval. First-order validation exercises with the deduced 1992-1999 time series of stage fluctuations reveal accuracies ranging from tens of centimeters to several meters (mean ˜1.1 m rms). Altimetric water levels in the Solimões and Amazon are particularly well defined with amplitudes <13 m and variations in peak-level timing from May to July. The water-surface gradient of the main stem is found to vary both spatially and temporally, with values ranging from 1.5 cm/km downstream to 4.0 cm/km for more upstream reaches. In agreement with ground-based estimates, the seasonal variability of the gradients reveals that the hysteresis characteristic of the flood wave varies along the main stem and the derived altimetric velocity of this flood wave is estimated to be ˜0.35 m/s. Overall, the altimetric results demonstrate that the T/P mission is successfully monitoring the transient flood waves of this continental-scale river basin.
... to be freshly formed and are too small to be significantly af-fected by riming and aerosolsca... more ... to be freshly formed and are too small to be significantly af-fected by riming and aerosolscavenging processes. ... are detected and opti-cally sized using the transit time between two continuous 532nm frequency-doubled neodymium-doped yttrium alu-minum garnet (Nd:YAG ...
Availability and utilization of computed tomography angiography has been increasing recently. We ... more Availability and utilization of computed tomography angiography has been increasing recently. We aimed to assess the effectiveness of low amount of contrast media and low kV value in order to reduce possible side effects of contrast media and to provide optimization of kV value in the evaluation of the carotid artery with multi-detector computed tomography angiography. Forty one patients were randomized into two groups. Contrast media was administered at a dose of 1 ml/kg in group A patients and of 0.5 ml/kg in group B patients. kV value of 120 in group A and 100 in group B were chosen. Bolus tracking technique was used. Attenuation values of certain arterial segments were measured, and values over 200 HU were considered as significant. North American Symptomatic Carotid Endartherectomy Trial criteria were utilized in the evaluation of stenosis. Image quality in arterial segments of all cases was found to be sufficient for diagnosis. Arterial attenuation values were found to be higher in group B than group A. When compared separately in all arterial segments, there was no statistically significant difference between the groups. For stenosis, 615 arterial segments were evaluated. Moderate stenosis in eight segments and severe stenosis in three segments were identified in group A. Occlusion in three segments, severe stenosis in three segments, and moderate stenosis in 25 segments were detected in group B. Better image quality can be obtained, and the amount of contrast media can be reduced using low kV technique in carotid artery multi-detector computed tomography angiography examination.
Letters to the Editor are welcomed. They may report new clinical or laboratory observations and n... more Letters to the Editor are welcomed. They may report new clinical or laboratory observations and new developments in medical care or may contain comments on recent contents of the Journal. They will be published, if found suitable, as space permits. Like other material ...
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