Trends in nontariff barriers of developed countries : 1966-1986

While major concerns have been expressed about the spread of non-tariff barriers (NTBs) in developing countries, the lack of empirical information on the dimensions of the increase has affected the related policy debates. Using inventories of NTBs in developed countries compiled for 1966 and 1986, this study develops quantitative information on the major expansions of NTBs that occurred over this 20 year period. The paper finds that in 1966 NTBs affected 25 percent of developed countries imports, while in 1986 this share has increased to 48 percent. A second major point documented in the study is that the spread of NTBs has been uneven across countries and industrial sectors. Third, this study shows that the increased resort to discriminatory NTBs like"voluntary"export restraints (particularly in the U.S.) caused a significantly higher share of trade to be"affected"by NTBs than suggested by commonly used trade coverage ratios. The findings concerning the extent that NTBs have proliferated in some sectors (and countries) also increases the importance of establishing effective procedures for liberalization of these measures in multilateral trade negotiations like the Uruguay Round.Environmental Economics&Policies,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Trade Policy,Transport and Trade Logistics

Proof Complexity of Systems of (Non-Deterministic) Decision Trees and Branching Programs

This paper studies propositional proof systems in which lines are sequents of decision trees or branching programs, deterministic or non-deterministic. Decision trees (DTs) are represented by a natural term syntax, inducing the system LDT, and non-determinism is modelled by including disjunction, ?, as primitive (system LNDT). Branching programs generalise DTs to dag-like structures and are duly handled by extension variables in our setting, as is common in proof complexity (systems eLDT and eLNDT). Deterministic and non-deterministic branching programs are natural nonuniform analogues of log-space (L) and nondeterministic log-space (NL), respectively. Thus eLDT and eLNDT serve as natural systems of reasoning corresponding to L and NL, respectively. The main results of the paper are simulation and non-simulation results for tree-like and dag-like proofs in LDT, LNDT, eLDT and eLNDT. We also compare them with Frege systems, constant-depth Frege systems and extended Frege systems

Reducing Uncertainties in the Production of the Gamma Emitting Nuclei 26Al, 44Ti, and 60Fe in Core Collapse Supernovae by Using Effective Helium Burning Rates

We have used effective reaction rates (ERR) for the helium burning reactions to predict the yield of the gamma-emitting nuclei 26Al, 44Ti, and 60Fe in core col- lapse supernovae. The variations in the predicted yields for values of the reaction rates allowed by the ERR are much smaller than obtained previously, and smaller than other uncertainties. A "filter" for supernova nucleosynthesis yields based on pre-supernova structure was used to estimate the effect of failed supernovae on the initial mass function-averaged yields; this substantially reduced the yields of all these isotopes, but the predicted yield ratio 60Fe/26Al was little affected. The robustness of this ratio is promising for comparison with data, but it is larger than observed in nature; possible causes for this discrepancy are discussed.Comment: 16 pages, 3 figure

A Future of Failure? The Flow of Technology Talent into Government and Civil Society

This report is an evaluation of the technology talent landscape shows a severe paucity of individuals with technical skills in computer science, data science, and the Internet or other information technology expertise in civil society and government. It investigates broadly the health of the talent pipeline that connects individuals studying or working in information technology-related disciplines to careers in public sector and civil society institutions. Barriers to recruitment and retention of individuals with the requisite skills include compensation, a perceived inability to pursue groundbreaking work, and cultural aversion to innovation

Root system chip-firing II: Central-firing

Jim Propp recently proposed a labeled version of chip-firing on a line and conjectured that this process is confluent from some initial configurations. This was proved by Hopkins-McConville-Propp. We reinterpret Propp's labeled chip-firing moves in terms of root systems: a "central-firing" move consists of replacing a weight $\lambda$ by $\lambda+\alpha$ for any positive root $\alpha$ that is orthogonal to $\lambda$. We show that central-firing is always confluent from any initial weight after modding out by the Weyl group, giving a generalization of unlabeled chip-firing on a line to other types. For simply-laced root systems we describe this unlabeled chip-firing as a number game on the Dynkin diagram. We also offer a conjectural classification of when central-firing is confluent from the origin or a fundamental weight.Comment: 30 pages, 6 figures, 1 table; v2, v3: minor revision