Renegotiation of transportation public-private partnerships: The US experience

Public-private partnerships (P3s) typically rely on long-term contracts between participants. When conditions arise that fall outside the expectations embodied in the contract, one party may seek to renegotiate the contract terms. Globally, the frequency of P3 contract renegotiations has been sufficient to raise questions regarding why these events occur and what their consequences are for the projects and society. The literature highlights four relevant causes behind renegotiation occurrences: unexpected exogenous changes, the complexity of the contractual relationship, winner's curse and rent seeking behavior. This study examines the US experience with highway P3 renegotiations, including four types of event: contract modifications, defaults, bankruptcies and buyouts. While the US highway P3 market has grown gradually, failure to understand renegotiations and their potential consequences may dampen the market and adversely affect national infrastructure investment efforts. The analysis finds that insufficient evidence exists to disentangle the drivers of renegotiation in the US, although exogenous changes and contractual relationship complexity appear to be paramount. The analysis highlights the distinct political and institutional environment that shapes highway P3 renegotiations in the US, suggesting the need for continuing and sensible analysis to effectively manage the undesirable consequences of renegotiations

Do State Fiscal Constraints Affect Implementation of Highway Public-Private Partnerships? A Panel Fixed Logit Assessment

Infrastructure public-private partnerships (“P3s”) have gained considerable recognition as useful policy tools for state and local governments to deliver critically needed infrastructure projects. The objective of this study is to empirically test one of the claims often made regarding states’ motivations for employing this procurement mechanism: P3s can help overcome fiscal constraints on state infrastructure investment. In addition, this study empirically analyzes how state P3 enabling legislation affects the behavior of both the public and private sectors. A regular logit model and a fixed effects logit panel model are employed to test the hypothesis that states with more severe fiscal constraints are more likely to seek P3s for highway infrastructure construction and finance. After controlling for such factors as state economic condition, legislative political affiliation, and highway travel demand, the empirical results indicate that states’ fiscal constraints are not associated with the propensity to use highway P3 projects

Notable improvements on LWFA through precise laser wavefront tuning

Oumbarek Espinos D., Rondepierre A., Zhidkov A., et al. Notable improvements on LWFA through precise laser wavefront tuning. Scientific Reports 13, 18466 (2023); https://doi.org/10.1038/s41598-023-45737-5.Laser wakefield acceleration (LWFA) continues to grow and awaken interest worldwide, especially as in various applications it approaches performance comparable to classical accelerators. However, numerous challenges still exist until this can be a reality. The complex non-linear nature of the process of interaction between the laser and the induced plasma remains an obstacle to the widespread LWFA use as stable and reliable particle sources. It is commonly accepted that the best wavefront is a perfect Gaussian distribution. However, experimentally, this is not correct and more complicated ones can potentially give better results. in this work, the effects of tuning the laser wavefront via the controlled introduction of aberrations are explored for an LWFA accelerator using the shock injection configuration. Our experiments show the clear unique correlation between the generated beam transverse characteristics and the different input wavefronts. The electron beams stability, acceleration and injection are also significantly different. We found that in our case, the best beams were generated with a specific complex wavefront. A greater understanding of electron generation as function of the laser input is achieved thanks to this method and hopes towards a higher level of control on the electrons beams by LWFA is foreseen

Do State Fiscal Constraints Affect Implementation of Highway Public-Private Partnerships? A Panel Fixed Logit Assessment

Infrastructure public-private partnerships (“P3s”) have gained considerable recognition as useful policy tools for state and local governments to deliver critically needed infrastructure projects. The objective of this study is to empirically test one of the claims often made regarding states’ motivations for employing this procurement mechanism: P3s can help overcome fiscal constraints on state infrastructure investment. In addition, this study empirically analyzes how state P3 enabling legislation affects the behavior of both the public and private sectors. A regular logit model and a fixed effects logit panel model are employed to test the hypothesis that states with more severe fiscal constraints are more likely to seek P3s for highway infrastructure construction and finance. After controlling for such factors as state economic condition, legislative political affiliation, and highway travel demand, the empirical results indicate that states’ fiscal constraints are not associated with the propensity to use highway P3 projects

Laser-plasma electron acceleration towards a compact XFEL in Japan

In Japan we are conducting a laser-plasma acceleration (LPA) project aiming a compact X-ray free-electron laser (XFEL) system and a compact carbon ion injector for cancer therapy including efficient laser driver development. In this talk we will focus on the laser electron acceleration part. Our LPA electron beam platform is located in the SPring-8 Center site at RIKEN, Japan, where the prototype XFEL of SACLA was tested. In the platform a Ti:sapphire laser system is installed and it can deliver three synchronized laser pulses (~20 – 30 fs) with pulse energies of 1 J, 2 J, and 10 J. Our strategy is staged electron acceleration using these pulses by manipulating electron phase space to obtain monoenergetic electron beams.In this talk we present our recent results on ~250 MeV, reproducible, quasi-monoenergetic electron production, undulator radiation test, etc.*This work was supported by JST-Mirai Program Grant Number JPMJMI17A1, Japan.IAS Program on High Energy Physics (HEP 2021

Towards a compact X-ray free-electron laser based on laser-accelerated electron beams

In the presentation, we show the design and our approach to achieve soft X-ray free-electron lasers (FELs) by using staged laser plasma acceleration (LPA) of electrons.The staged LPA consists of several functionalized stages such as electron injector, phase rotation, and energy booster to manipulate electron beams to satisfy the requirements for an XFEL. This is a challenging task but this scheme has a favorable scaling to higher energies and has larger tuningknobs to manipulate electron beam quality.11th International Conference on Inertial Fusion Sciences and Application