Apply GNSS-Reflectometry Technique for wind retrieval in typhoon condition

Global Navigation Satellite System-Reflectometry (GNSS-R) is an innovative Earth observation technique that exploits signal from satellite constellations after reflection on the Eart h surface. The GNSS-R techniques is also known to have the potential of mapping the surface wind speed up to 70 m/s, and thus provide a promising solution. Abundant real-time data of the typhoon surface wind speed will play the crucial role on the improvement of typhoon intensification forecasting. The aim of present study is to investigate the influences of high wind speed and the corresponding giant waves during typhoon to the GNSS-R wind speed retrieval algorithms. The Mean Square Slope that altered by the complex wave directionality is discussed. Finally, the uncertainties of wind speed retrieval with respect to the influences of wave directionality is assessed. The level 1 product from the GNSS-R receiver is a map of GPS signal power scattered from the sea surface, as a 2D function of delay and Doppler frequency, which is known as a Delay-Doppler Map, or DDM. Based on Zavorotny-Voronovich model, the DDMs are simulated from the Directional Mean Square Slope (DMSS) that obtained from the combination of capillary wave spectra and gravity wave spectra. The gravity wave spectra were calculated using a 3rd generation numerical wave model that driven by the Dujuan typhoon (2015) wind fields with super-fine resolution. The complexity of directional wave spectrum, such as extreme spatial heterogeneity, bimodal spectra and varying directional spreading alter the DMSS and DDM. Various observables, e.g. DDM Average (DDMA), and Leading Edge Slope (LES) are then applied to the simulated DDM. Regression-based wind retrievals are developed for each individual observable using empirical geophysical model functions. The wind speed retrieval in case of Dujuan typhoon are compared with the target data uncertainty assessment

Ray Tracing Simulation in Nonspherically Symmetric Atmosphere for GPS Radio Occultation

A three-dimensional ray tracing model with aiming algorithms for global positioning system (GPS) signal is proposed to make simulations conform to the realistic radio occultation (RO) signal propagation. The two aiming algorithms used in this study ensure the initial and end point ray trajectories are located in the prescribed region. In past studies, the ray tracing techniques applied to the RO signal simulation usually assumed a spherically symmetrical atmosphere for simplicity. The exact GPS and low earth orbit (LEO) satellite locations are not considered in the simulation. These two assumptions make the simulation unrealistic for GPS signal propagation in the RO technique. In the proposed model, the shape of the earth is assumed as an ellipse. The information from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis is used to setup the atmosphere in the simulation. Two aiming algorithms are developed to determine the initial signal propagating direction to make the simulated signal start from the prescribed GPS satellite position and end in the close vicinity of the LEO satellite position. An ideal spherical symmetric atmospheric structure is used to verify the ray tracing model. The fractional difference between real and simulated refractivity results is less than 0.1%. Otherwise, the GPS and LEO satellite position in the Formosat-3/COSMIC observation and the ECMWF analysis, considering the earth¡¦s flattening, is also used to verify the aiming algorithms. All of the simulated signals end in close vicinity to the LEO satellite position in the simulation results

Hungry bone syndrome in peritoneal dialysis patients after parathyroid surgery

Secondary hyperparathyroidism (SHPT) is a common complication of end-stage kidney disease (ESKD). Hungry bone syndrome (HBS) occurs frequently in patients on maintenance dialysis receiving parathyroidectomy for refractory SHPT. However, there is scanty study investigating the clinical risk factors that predict postoperative HBS, and its outcome in peritoneal dialysis (PD) patients. We conducted a single-center retrospective study to analyze 66 PD patients who had undergone parathyroidectomy for secondary hyperparathyroidism at Chang Gung Memorial Hospital between 2009 and 2019. The patients were stratified into two groups based on the presence ( n=47) or absence (n=19) of HBS after parathyroidectomy. Subtotal parathyroidectomy was the most common surgery performed (74.2%), followed by total parathyroidectomy with autoimplantation (25.8%). Pathological examination of all surgical specimens revealed parathyroid hyperplasia (100%). Patients with HBS had lower levels of postoperative nadir corrected calcium, higher alkaline phosphate (ALP), and higher potassium levels compared with patients without HBS (all P<0.05). A multivariate logistic regression model confirmed that lower preoperative serum calcium level (OR 0.354, 95% CI 0.133–0.940, P=0.037), higher ALP (OR 1.026, 95% CI 1.008–1.044, P=0.004), and higher potassium level (OR 6.894, 95% CI 1.806–26.317, P=0.005) were associated with HBS after parathyroidectomy. Patients were followed for 58.2±30.8 months after the surgery. There was no significant difference between HBS and non-HBS groups in persistence (P=0.496) or recurrence (P=1.000) of hyperparathyroidism. The overall mortality rate was 10.6% with no significant difference found between both groups (P=0.099). We concluded that HBS is a common complication (71.2%) of parathyroidectomy for SHPT and should be managed appropriately

GT-repeat polymorphism in the heme oxygenase-1 gene promoter and the risk of carotid atherosclerosis related to arsenic exposure

<p>Abstract</p> <p>Background</p> <p>Arsenic is a strong stimulus of heme oxygenase (HO)-1 expression in experimental studies in response to oxidative stress caused by a stimulus. A functional GT-repeat polymorphism in the HO-1 gene promoter was inversely correlated to the development of coronary artery disease in diabetics and development of restenosis following angioplasty in patients. The role of this potential vascular protective factor in carotid atherosclerosis remains unclear. We previously reported a graded association of arsenic exposure in drinking water with an increased risk of carotid atherosclerosis. In this study, we investigated the relationship between HO-1 genetic polymorphism and the risk of atherosclerosis related to arsenic.</p> <p>Methods</p> <p>Three-hundred and sixty-seven participants with an indication of carotid atherosclerosis and an additional 420 participants without the indication, which served as the controls, from two arsenic exposure areas in Taiwan, a low arsenic-exposed Lanyang cohort and a high arsenic-exposed LMN cohort, were studied. Carotid atherosclerosis was evaluated using a duplex ultrasonographic assessment of the extracranial carotid arteries. Allelic variants of (GT)n repeats in the 5'-flanking region of the HO-1 gene were identified and grouped into a short (S) allele (< 27 repeats) and long (L) allele (≥ 27 repeats). The association of atherosclerosis and the HO-1 genetic variants was assessed by a logistic regression analysis, adjusted for cardiovascular risk factors.</p> <p>Results</p> <p>Analysis results showed that arsenic's effect on carotid atherosclerosis differed between carriers of the class S allele (OR 1.39; 95% CI 0.86-2.25; <it>p </it>= 0.181) and non-carriers (OR 2.65; 95% CI 1.03-6.82; <it>p </it>= 0.044) in the high-exposure LMN cohort. At arsenic exposure levels exceeding 750 μg/L, difference in OR estimates between class S allele carriers and non-carriers was borderline significant (<it>p </it>= 0.051). In contrast, no such results were found in the low-exposure Lanyang cohort.</p> <p>Conclusions</p> <p>This exploratory study suggests that at a relatively high level of arsenic exposure, carriers of the short (GT)n allele (< 27 repeats) in the HO-1 gene promoter had a lower probability of developing carotid atherosclerosis than non-carriers of the allele after long-term arsenic exposure via ground water. The short (GT)n repeat in the HO-1 gene promoter may provide protective effects against carotid atherosclerosis in individuals with a high level of arsenic exposure.</p

Association of clinical symptomatic hypoglycemia with cardiovascular events and total mortality in type 2 diabetes a nationwide population-based study

OBJECTIVE Hypoglycemia is associated with serious health outcomes for patients treated for diabetes. However, the outcome of outpatients with type 2 diabetes who have experienced hypoglycemia episodes is largely unknown. RESEARCH DESIGN AND METHODS The study population, derived from the National Health Insurance Research Database released by the Taiwan National Health Research Institutes during 1998–2009, comprised 77,611 patients with newly diagnosed type 2 diabetes. We designed a prospective study consisting of randomly selected hypoglycemic type 2 diabetic patients and matched type 2 diabetic patients without hypoglycemia. We investigated the relationships of hypoglycemia with total mortality and cardiovascular events, including stroke, coronary heart disease, cardiovascular diseases, and all-cause hospitalization. RESULTS There were 1,844 hypoglycemic events (500 inpatients and 1,344 outpatients) among the 77,611 patients. Both mild (outpatient) and severe (inpatient) hypoglycemia cases had a higher percentage of comorbidities, including hypertension, renal diseases, cancer, stroke, and heart disease. In multivariate Cox regression models, including diabetes treatment adjustment, diabetic patients with hypoglycemia had a significantly higher risk of cardiovascular events during clinical treatment periods. After constructing a model adjusted with propensity scores, mild and severe hypoglycemia still demonstrated higher hazard ratios (HRs) for cardiovascular diseases (HR 2.09 [95% CI 1.63–2.67]), all-cause hospitalization (2.51 [2.00–3.16]), and total mortality (2.48 [1.41–4.38]). CONCLUSIONS Symptomatic hypoglycemia, whether clinically mild or severe, is associated with an increased risk of cardiovascular events, all-cause hospitalization, and all-cause mortality. More attention may be needed for diabetic patients with hypoglycemic episodes.Pai-Feng Hsu, Shih-Hsien Sung, Hao-Min Cheng, Jong-Shiuan Yeh, Wen-Ling Liu, Wan-Leong Chan, Chen-Huan Chen, Pesus Chou, Shao-Yuan Chuan