851 research outputs found
On the Welfare of Cardinal Voting Mechanisms
No full textA voting mechanism is a method for preference aggregation that takes as input preferences over alternatives from voters, and selects an alternative, or a distribution over alternatives. While preferences of voters are generally assumed to be cardinal utility functions that map each alternative to a real value, mechanisms typically studied assume coarser inputs, such as rankings of the alternatives (called ordinal mechanisms). We study cardinal mechanisms, that take as input the cardinal utilities of the voters, with the objective of minimizing the distortion - the worst-case ratio of the best social welfare to that obtained by the mechanism.
For truthful cardinal mechanisms with m alternatives and n voters, we show bounds of Theta(mn), Omega(m), and Omega(sqrt{m}) for deterministic, unanimous, and randomized mechanisms respectively. This shows, somewhat surprisingly, that even mechanisms that allow cardinal inputs have large distortion. There exist ordinal (and hence, cardinal) mechanisms with distortion O(sqrt{m log m}), and hence our lower bound for randomized mechanisms is nearly tight. In an effort to close this gap, we give a class of truthful cardinal mechanisms that we call randomized hyperspherical mechanisms that have O(sqrt{m log m}) distortion. These are interesting because they violate two properties - localization and non-perversity - that characterize truthful ordinal mechanisms, demonstrating non-trivial mechanisms that differ significantly from ordinal mechanisms.
Given the strong lower bounds for truthful mechanisms, we then consider approximately truthful mechanisms. We give a mechanism that is delta-truthful given delta in (0,1), and has distortion close to 1. Finally, we consider the simple mechanism that selects the alternative that maximizes social welfare. This mechanism is not truthful, and we study the distortion at equilibria for the voters (equivalent to the Price of Anarchy, or PoA). While in general, the PoA is unbounded, we show that for equilibria obtained from natural dynamics, the PoA is close to 1. Thus relaxing the notion of truthfulness in both cases allows us to obtain near-optimal distortion
Recent trends in postcystectomy health-related Quality of Life (QoL) favors neobladder diversion: Systematic Review of the Literature
No full textThe study aims to review the current evidence for quality of life posturinary diversion surgery comparing neobladder to other types of diversion. A review of literature from inception to July 2015 for all English-language articles was done. Based on our inclusion criteria, 22 studies (2450 patients) were included. Whereas none of the prospective studies showed any quality of life (QoL) advantage with ileal conduit diversion, 3 of the 5 prospective studies and 4 of the 6 studies published after 2011 show better QoL outcomes with neobladder than other urinary diversion types. All prospective studies published after 2011 have shown neobladder to have superior QoL outcomes than its comparators. Recent trends indicate that orthotopic neobladder postcystectomy is associated with better QoL outcomes compared to other urinary diversion types.</p
Safety and feasibility of day case ureteroscopy and laser lithotripsy (URSL) in patients with a solitary kidney
No full textINTRODUCTION: The management of nephrolithiasis in patients with a solitary kidney poses a treatment challenge. The study aimed to evaluate the outcomes of ureteroscopy and laser stone fragmentation (URSL) for renal stones in these patients treated in our university teaching hospital.MATERIAL AND METHODS: Between July 2012 and December 2014, seventeen cases of URSL for stones in a solitary kidney were reviewed. Patient demographics, stone dimensions, perioperative and post-operative outcomes were recorded in a prospectively maintained database. Serum creatinine levels pre-procedure and at follow-up were also compared.RESULTS: Seventeen cases of URSL were conducted with a mean age of 52.9 ±19.9 years. 8 of the 17 (47%) patients had stones in multiple locations and 13 (76%) were in the lower pole. The mean ± SD stone size and BMI were 13.0 ±8.9 mm and 31.6 ±5.8 kg/m(2), respectively. The stone free rate (SFR) was 82.5%. Fourteen (82.5%) patients were discharged the same day and 16 cases (94%) were discharged within 24 hours. For patients with deranged pre-operative serum creatinine, the mean serum creatinine level improved from 131.2 ±68.3 µmol/L pre-URSL to 106.5 ±36.7 µmol/L at follow-up. There was one Clavien grade II complication with a patient requiring additional antibiotics for post-operative urinary tract infection. There were no other major or minor complications.CONCLUSIONS: Day case ureteroscopy for stone disease in a solitary kidney is safe and feasible with a low complication rate and an overall improvement in renal function.</p
Moral hazard and private monitoring.
No full text1This paper incorporates earlier work by Bhaskar [4] and unpublished notes by van Damme. We are grateful to Tilman Börgers, Dilip Mookherjee, Debraj Ray, an anonymous referee, an associate editor, and numerous seminar audiences for useful comments. The first author thanks the CentER for Economic Research (Tilburg) for its hospitality while some of this research was carried out.
Distributed hole detection algorithms for wireless sensor networks
No full textWe present two novel distributed algorithms for hole detection in a wireless sensor network (WSN) based on the distributed Delaunay triangulation of the underlying communication graph. The first, which we refer to as the distance-vector hole determination (DVHD) algorithm, is based on traditional distance vector routing for multi-hop networks and shortest path lengths between node pairs. The second, which we refer to as the Gaussian curvature-based hole determination (GCHD) algorithm, applies the Gauss-Bonnet theorem on the Delaunay graph to calculate the number of holes based on the graph's Gaussian curvature. We present a detailed comparative performance analysis of both methods based on simulations, showing that while DVHD is conceptually simpler, the GCHD algorithm shows better performance with respect to run-time and message count per node
Book Review: Partha S. Ghosh, Migrants, Refugees and the Stateless in South Asia
No full text Partha S. Ghosh, Migrants, Refugees and the Stateless in South Asia. New Delhi: SAGE Publications India, 2016, Hardback, 384 pp., ₹995, ISBN-13: 978-9351508540. </jats:p
Results of day-case ureterorenoscopy (DC-URS) for stone disease: prospective outcomes over 4.5 years
No full textPURPOSE: To investigate the prospective outcomes of day-case ureterorenoscopy (DC-URS) for stone disease. With the rising prevalence of stone disease in the face of finite resources, there is increasing pressure to undertake procedures as a day case avoiding in-patient stay. There are a limited number of studies reporting on the feasibility of ureteroscopy as a day-case procedure. This study aimed to investigate the prospective outcomes and predictors precluding to DC-URS for stone disease in patients treated in our university teaching hospital.MATERIALS AND METHODS: Between March 2012 and July 2016, consecutive cases of adult stone ureteroscopy performed or supervised by a single surgeon were recorded in a prospective database. Patients underwent pre-operative counselling in a specialist stone clinic and were admitted to a dedicated 'Surgical day unit' on the day of surgery. A standardised anaesthetic protocol was adhered to in all cases. Data on patient demographics, stone parameters, pre-operative assessment, operative details, length of stay, stone-free rate and complication rates were collected and analysed.RESULTS: A total of 544 consecutive adult ureteroscopy for stone disease were conducted over the study period with a day-case rate of 77.7%. Thirty-nine percent of failed day-case ureteroscopy were due to late completion of ureteroscopy and due to associated social circumstances of patients. The mean stone size, operating time duration and post-operative stent insertion rates for DC-URS patients were 14 mm, 46 min and 96.5%, respectively. Post-operatively, the mean stone-free rate (SFR), unplanned re-admissions and complications for DC-URS patients were 95, 4 and 4%, respectively. A higher failure of DC-URS was related to patient's age (p = 0.003), positive pre-operative urine culture (p < 0.001), elevated pre-operative serum creatinine (p < 0.001) and higher mean operating time (p < 0.02).CONCLUSION: Based on our results, a day-case ureteroscopy rate of nearly 78% can be achieved. With its acceptable complication rate, and low re-admission rates, DC-URS is a safe and feasible option in a majority of patients with stone disease.</p
Successful ureteroscopy for kidney stone disease leads to resolution of urinary tract infections: Prospective outcomes with a 12-month follow-up
No full textIntroduction: To investigate the resolution of urinary tract infection (UTI) with the successful treatment of kidney stone disease (KSD).We reviewed the outcomes of ureteroscopy (URS) and stone treatment for patients with positive urine culture or recurrent UTIs and evaluated whether the infection resolved with the clearance of their urinary stones.Material and methods: Between March 2012 and July 2016, consecutive patients who underwent URS for stone disease with a history of recurrent UTIs or culture proven UTIs were identified from a prospective database. Data was recorded on stone free rate (SFR) and infection free rate (IFR) during the follow-up period at 3, 6 and 12-months.Results: During the study period, 103 consecutive patients with stone disease and associated UTI underwent URS over a 52-month period (mean age: 60 years, Female: Male ratio of 2:1). The mean cumulative stone size was 16 mm (range: 3-107 mm) and a positive pre-operative urine culture was found in 81 (79%) patients. While the overall SFR was 96%, the total complication rate was 12.6% (n = 13) and these were all Clavien I/II complications.At follow-up, the SFR and IFR was 96% and 88% at 3-months, and 82% and 71% at 12-months, respectively (p <0.001). While almost three-quarters of patients were stone and infection free at 12-months, the majority of those with stones recurrence also had recurrence of their UTI.Conclusions: The majority of patients will remain infection free at the 12-month follow-up if they are stone free after their initial treatment. Stone recurrence, which is more likely in high-risk patients, is also linked to the recurrence of their UTI.</p
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