The simple micro-economics of public-private partnerships

We build a unified theoretical framework to analyze the main incentive issues in Public Private Partnerships (PPPs) and the shape of optimal contracts in those contexts. We present a basic model of procurement in a multitask environment in which a risk-averse agent chooses unobservable efforts in cost reduction and quality improvement. We begin by studying the effect on incentives and risk transfer of bundling building and operation into a single contract, allowing for different assumptions on the contractual framework and the quality of the information held by the government. We then extend the basic model in several directions. We consider the factors that affect the optimal allocation of demand risk and their implications for the use of user charges and the choice of contract length. We study the relationship between the operator and its financiers and the impact of private finance. We discuss the trade-off between incentive and flexibility in long-term PPP agreements and the dynamics of PPP contracts, including cost overruns. We also consider how the institutional environment, and specifically the risk of regulatory opportunism, affects contract design and incentives. We conclude with some policy implications on the desirability of PPPs

The theory of incentives applied to the transport sector

Building upon Iossa and Martimort (2008), we study the main incentive issues and the form of optimal contracts for Public Private Partnerships (PPPs) in transports. We present a basic model of procurement in a multitask environment in which a risk-averse firm chooses unobservable efforts in infrastructure and service quality. We begin by analyzing the effect on incentives and risk transfer of bundling building and operation into a single contract. We consider the factors that affect the optimal allocation of demand risk and their implications for the choice of contract length. We discuss the dynamics of PPP contracts and how the risk of regulatory opportunism affects contract design and incentives

Exact solution of Kerr black hole perturbations via CFT2 and instanton counting: Greybody factor, quasinormal modes, and Love numbers

We give explicit expressions for the finite frequency greybody factor, quasinormal modes, and Love numbers of Kerr black holes by computing the exact connection coefficients of the radial and angular parts of the Teukolsky equation. This is obtained by solving the connection problem of the confluent Heun equation in terms of the explicit expression of irregular Virasoro conformal blocks as sums over partitions via the Alday, Gaiotto, and Tachikawa correspondence. In the relevant approximation limits our results are in agreement with existing literature. The method we use can be extended to solve the linearized Einstein equation in other interesting gravitational backgrounds

Overfeeding Reduces Insulin Sensitivity and Increases Oxidative Stress, without Altering Markers of Mitochondrial Content and Function in Humans

BACKGROUND: Mitochondrial dysfunction and increased oxidative stress are associated with obesity and type 2 diabetes. High fat feeding induces insulin resistance and increases skeletal muscle oxidative stress in rodents, but there is controversy as to whether skeletal muscle mitochondrial biogenesis and function is altered. METHODOLOGY AND PRINCIPAL FINDINGS: Forty (37±2 y) non-obese (25.6±0.6 kg/m2) sedentary men (n = 20) and women (n = 20) were overfed (+1040±100 kcal/day, 46±1% of energy from fat) for 28 days. Hyperinsulinemic-euglycemic clamps were performed at baseline and day 28 of overfeeding and skeletal muscle biopsies taken at baseline, day 3 and day 28 of overfeeding in a sub cohort of 26 individuals (13 men and 13 women) that consented to having all 3 biopsies performed. Weight increased on average in the whole cohort by 0.6±0.1 and 2.7±0.3 kg at days 3 and 28, respectively (P<0.0001, without a significant difference in the response between men and women (P = 0.4). Glucose infusion rate during the hyperinsulinemic-euglycemic clamp decreased from 54.8±2.8 at baseline to 50.3±2.5 mmol/min/kg FFM at day 28 of overfeeding (P = 0.03) without a significant difference between men and women (P = 0.4). Skeletal muscle protein carbonyls and urinary F2-isoprostanes increased with overfeeding (P,<.05). Protein levels of muscle peroxisome proliferator-activated receptor gamma coactivator-1a (PGC1a) and subunits from complex I, II and V of the electron transport chain were increased at day 3 (all P<0.05) and returned to basal levels at day 28. No changes were detected in muscle citrate synthase activity or ex vivo CO2 production at either time point. CONCLUSIONS: Peripheral insulin resistance was induced by overfeeding, without reducing any of the markers of mitochondrial content that were examined. Oxidative stress was however increased, and may have contributed to the reduction in insulin sensitivity observed.Dorit Samocha-Bonet, Lesley V. Campbell, Trevor A. Mori, Kevin D. Croft, Jerry R. Greenfield, Nigel Turner and Leonie K. Heilbron

International mammal trapping standards ̶ Part II: Killing Trap Systems

In this paper, we propose standards for killing trap systems based on Proulx et al.’s (2022) prerequisites, which provide context and explanations for our approach. Our aim is to identify assessment protocols that are based on the scientific method, and that include evaluation parameters and threshold levels of acceptation, and laboratory and field procedures, to recognize mammal trapping systems that are acceptable from an animal welfare, and capture efficiency and selectivity, point of view. The testing of killing trap systems consists of 4 steps: 1) Mechanical evaluation; 2) Approach tests in semi-natural environments; 3) Kill tests in semi-natural environments; and 4) Kill tests on traplines. Based on the normal approximation to the binomial distribution, acceptable killing trap systems are expected, at a 95% confidence level, to render ≥85% of the animals irreversibly unconscious in ≤ 90 sec for most mammal species, and ≤30 sec for small mammals (mouse, vole, etc.). We recommend that standards be continuously updated based on the development of new designs and technology