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Abstract. An authenticated group key exchange (AGKE) scheme allows a group of users in a public network to share a session key which may later be used to achieve desirable cryptographic goals. In the paper, we study AGKE schemes for dynamically changing groups in ad hoc networks, i.e., for environments such that a member of a group may join and/or leave at any given time and a group key is exchanged without the help of any central sever. Difficulties in group key managements under such environments are caused by dynamically changing group and existence of no trustee. In most AGKE schemes proposed so far in the literature, the number of rounds is linear with respect to the number of group members. Such schemes are neither scalable nor practical since the number of group members may be quite large and the efficiency of the schemes is severely degraded with only one member's delay. We propose an efficient provably secure AGKE scheme with constant-round. The propose scheme is still contributory and efficient, where each user executes three modular exponentiations and at most O(n) XOR operations.Keyword. dynamic authenticated group key exchange, ad hoc networks.

IntroductionInitial lactate level, lactate clearance, C-reactive protein, and procalcitonin in critically ill patients with sepsis are associated with hospital mortality. However, no study has yet discovered which factor is most important for mortality in severe sepsis patients with lactic acidosis. We sought to clarify this issue in patients with lactic acidosis who were supplementing with sodium bicarbonate.Materials and MethodsData were collected from a single center between May 2011 and April 2014. One hundred nine patients with severe sepsis and lactic acidosis who were supplementing with sodium bicarbonate were included.ResultsThe 7-day mortality rate was 71.6%. The survivors had higher albumin levels and lower SOFA, APACHE II scores, vasopressor use, and follow-up lactate levels at an elapsed time after their initial lactate levels were checked. In particular, a decrement in lactate clearance of at least 10% for the first 6 hours, 24 hours, and 48 hours of treatment was more dominant among survivors than non-survivors. Although the patients who were treated with broad-spectrum antibiotics showed higher illness severity than those who received conventional antibiotics, there was no significant mortality difference. 6-hour, 24-hour, and 48-hour lactate clearance (HR: 4.000, 95% CI: 1.309–12.219, P = 0.015) and vasopressor use (HR: 4.156, 95% CI: 1.461–11.824, P = 0.008) were significantly associated with mortality after adjusting for confounding variables.ConclusionsLactate clearance at a discrete time point seems to be a more reliable prognostic index than initial lactate value in severe sepsis patients with lactic acidosis who were supplementing with sodium bicarbonate. Careful consideration of vasopressor use and the initial application of broad-spectrum antibiotics within the first 48 hours may be helpful for improving survival, and further study is warranted.

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The high incidence of cardiovascular disease and vitamin D deficiency in chronic kidney disease patients is well known. Vitamin D activation by omega-3 fatty acid (FA) supplementation may explain the cardioprotective effects exerted by omega-3 FA. We hypothesized that omega-3 FA and 25-hydroxyvitamin D (25(OH)D) supplementation may increase 1,25-dihydroxyvitamin D (1,25(OH)2D) levels compared to 25(OH)D supplementation alone in hemodialysis (HD) patients that have insufficient or deficient 25(OH)D levels. We enrolled patients that were treated for at least six months with 25(OH)D < 30 ng/mL (NCT01596842). Patients were randomized to treatment for 12 weeks with cholecalciferol supplemented with omega-3 FA or a placebo. Levels of 25(OH)D and 1,25(OH)2D were measured after 12 weeks. The erythrocyte membrane FA contents were also measured. Levels of 25(OH)D were increased in both groups at 12 weeks compared to baseline. The 1,25(OH)2D levels at 12 weeks compared to baseline showed a tendency to increase in the omega-3 FA group. The oleic acid and monounsaturated FA content decreased, while the omega-3 index increased in the omega-3 FA group. Omega-3 FA supplementation may be partly associated with vitamin D activation, although increased 25(OH)D levels caused by short-term cholecalciferol supplementation were not associated with vitamin D activation in HD patients.

BackgroundGuidelines recommend a break-in period of 2 weeks before starting peritoneal dialysis (PD), but PD within 14 days is also an acceptable and safe alternative to hemodialysis (HD) in patients with an urgent need. However, the effect of the break-in period within 48 hours or later had not been evaluated for early technical complications, long-term maintenance, and survival in patients starting urgent PD.MethodsOf 360 patients with a surgically inserted PD catheter, we evaluated 190 patients who needed urgent PD and 29 patients who received conventional PD at a single center between January 2007 and December 2014 in this retrospective observational study. Enrolled patients were divided according to break-in period of <48 hours (P1) or 2–13 days (P2) before starting urgent PD. The primary endpoint was incidence of early technical complications and secondary endpoints included long-term PD maintenance, and patient survival.ResultsPD was started in 103 patients (54.2%) within 48 hours and in 87 patients (45.8%) within 2 to 13 days. The incidence of early technical complication was significantly higher in P1 group (28.2%) than in P2 group (10.3%) (P = 0.002). The need for a repositioning procedure was significantly greater in P1 group (14.6%) than in P2 group (3.4%) (P = 0.009). However, we observed no significant differences between the two groups with respect to the prevalence of catheter dysfunction requiring change to HD within 6 months or incidence of peritonitis or exit-site infection. There was no significant difference in PD maintenance and patient survival according to the break-in period between P1 and P2 as well as against the control group.ConclusionUrgent PD was associated with a low incidence of early technical complications if start was avoided within 48 hours after catheter insertion, and long-term PD maintenance was independent of the break-in period.

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BackgroundThe effectiveness of dialysis on the incidence of cancer in patients with end-stage renal disease (ESRD) remains to be clarified. In this study, we evaluated the incidence rate and type of cancer among patients with ESRD, compared to the general population, through a prospective 7-year follow-up. We also calculated the cumulative incidence rate of cancer associated with ESRD, with stratification to control for the competing risk of death.MethodsThis prospective observational cohort study was conducted using data from a nationwide study on patients with ESRD in Korea. A total of 5,235 patients, ≥18 years old, with ESRD were identified from the national registry as being treated by dialysis between August 2008 and December 2014. The standardized incidence ratio (SIR) and cumulative incidence rate of specific cancers were evaluated and compared to the general population.ResultsA total of 5,235 participants were included. During the 7 year observation period, 116 (2.2%) participants had been diagnosed as cancer. The SIR of overall cancer was 0.94 [95% confidence interval (CI), 0.72–1.19] and was comparable to the rate for the general population. Although the digestive organs were the most frequent site of a primary site cancer (N = 39, 33.6%), the SIR was highest for urinary tract cancer [4.7, 95% CI, 2.42–8.19]. The five year standardized cumulative incidence of cancer was higher for females than for males, and for non-diabetic compared to diabetic causes of ESRD. We estimated that the five year standardized cumulative incidence was highest [8.4, 95% CI, 5.07–13.75] in patients with ESRD, caused by glomerulonephritis.ConclusionA screening program should be necessary for urinary tract cancer in Korean patients with ESRD. Cancer screening programs for patients with ESRD in Korea should be emphasized on female patients and patients with non-diabetic ESRD.