Optimal Auctions with Financially Constrained Bidders

We consider an environment where potential buyers of an indi- visible good have liquidity constraints, in that they cannot pay more than their `budget' regardless of their valuation. A buyer's valuation for the good as well as her budget are her private information. We derive constrained-efficient and revenue maximizing auctions for this setting. In general, the optimal auction requires `pooling' both at the top and in the middle despite the maintained assumption of a mono- tone hazard rate. Further, the auctioneer will never¯find it desirable to subsidize bidders with low budgets.the universal type space, the strategic topology; the uniform strategic topology; the uniform-weak topology; interim correlated rationalizable actions

Dominant Strategy Mechanisms with Multidimensional Types

This paper provides a characterization of dominant strategy mechanisms with quasi-linear utilities and multi-dimensional types for a variety of preference domains. These characterizations are in terms of a monotonicity property on the underlying allocation rule.Dominant Strategy, Farkas Lemma, Combinatorial Auctions.

Auction design with fairness concerns: Subsidies vs. set-asides

Government procurement and allocation programs often use subsidies and setasides favoring small businesses and other target groups to address fairness concerns. These concerns are in addition to standard objectives such as efficiency and revenue. We study the design of the optimal mechanism for a seller concerned with efficiency, subject to a constraint to favor a target group. In our model, buyers' private values are determined by costly pre-auction investment. If the constraint is distributional, i.e. to guarantee that the target group wins sufficiently often, then the constrained efficient mechanism is a flat subsidy. This is consistent with findings in the empirical literature. In contrast, if the constraint is to ensure a certain investment level by the target group, the optimal mechanism is a type dependent subsidy. In this case a set aside may be better than a flat or percentage subsidy

Role of multi detector computed tomography (MDCT) in evaluation of renal masses

Background: Due to rapid pace in development of imaging techniques and increasing number of investigations being done, more number of renal masses are discovered incidentally during evaluation of unrelated or unspecific symptoms. Hence it is vital to differentiate neoplastic and non-neoplastic masses. Among the neoplastic masses, there is a need to differentiate benign and malignant masses so that appropriate treatment strategies like nephron sparing surgery, radio frequency ablation etc. can be planned at an early stage and avoiding unnecessary radical treatments for improved patients survival.Methods: A Cross-sectional Observational study was done in 35 patients. Patients of either sex in any age group who had presented with suspected renal mass by clinical signs and symptoms (palpable renal angle mass, renal angle pain, hematuria) confirmed on USG examination or an incidental Renal mass diagnosed on USG/CT examination were included in our study.Results: Ultrasound is the initial imaging modality of choice since it is inexpensive, easy to perform and no radiation exposure. On USG, the renal lesions are classified as solid or cystic. Anechoic, thin walled cyst without any septations or solid components is usually Bosniak I cyst (simple cyst) and does not need any further evaluation. Rest of the cystic and solid lesions cannot be characterized by ultrasound and hence need further evaluation.Conclusions: Multidetector Computed Tomography is the imaging modality of choice for further evaluation and characterization. CT is done in four phases viz., unenhanced, corticomedullary, nephrographic and excretory phase especially in cases of malignancy while in benign conditions like angiomyolipoma and abscess, evaluation with unenhanced and single phase post contrast in portovenous phase is sufficient

Pressure-induced alpha-to-omega transition in titanium metal: A systematic study of the effects of uniaxial stress

We investigated the effects of uniaxial stress on the pressure-induced alpha-to-omega transition in pure titanium (Ti) by means of angle dispersive x-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa (argon pressure medium); (2) the a and w phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the w phase is affected by differences in the sample pressure environment; and (4) a short term laser-heating of Ti lowers the alpha-to-omega transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrated the influence of uniaxial stress in the alpha-to-omega transition.Comment: 16 pages, 6 figures, 1 tabl