Signal detection without finite-energy limits to quantum resolution

We show that there are extremely simple signal detection schemes where the finiteness of energy resources places no limit to the resolution. On the contrary, larger resolution can be obtained with lower energy. To this end the generator of the signal-dependent transformation encoding the signal information on the probe state must be different from the energy. We show that the larger the deviation of the probe state from being minimum-uncertainty state, the better the resolution.Comment: 5 pages, 3 figure

Access to Credit and the Effect of Credit Constraints on Costa Rican Manufacturing Firms

This paper examines the finances and the effect of credit limitations on the behavior and performance of firms in Costa Rica. The study is based on a survey of manufacturing firms conducted by the authors during 2001. The paper characterizes the profile firms’ finances, examines the determinants of firms’ access to banking credit and tries to assess the effect of credit constraints on the behavior and performance of firms. The paper finds that while banks are the main source of credit for larger firms, non-banking credit (trade plus informal credit) remains the leading source of funds for smaller firms. Moreover, own funds and informal credit is a leading form of credit for newly created firms. It is also found that the probability of having banking credit and the fraction of banking credit/total debt is mostly affected by (if anything) characteristics of the firm and not by those of their owners. Indeed, the firm’s value and age, and whether it keeps formal accounting procedures appear as the most relevant determinants of access to banking credit. With respect to the starting up finances of firms, the data is not conclusive on the determinants of banking credit, yet it suggests a negative relationship with the previous entrepreneurship experience of the owner. The paper discusses different explanations, all of which highlight the importance of credit constraints. Adopting ideas from the econometric literature on treatment effects, the paper explores the effect of banking credit on the behavior and performance of firms. Two different methods are used to correct for selection biases: a parametric two-step point method and a non-parametric method that estimates upper and lower bounds for the effects. While the results are not statistically conclusive, both methods do suggest that having access to banking credit positively affects firms’ performance.

Quality of Life in Urban Neighborhoods in Costa Rica

This paper considers valuation of amenities in urban neighborhoods and satisfaction with both those neighborhoods and life in general. First, rents are used to estimate neighborhood amenities price in San Jose, which explain 39 percent of the standardized variation of rents. Some districts rank very high in housing characteristics but poorly in neighborhood amenities, while others rank poorly in housing characteristics but high in neighborhood amenities, suggesting that indirect policy measures might reduce inequality in urban areas through improving neighborhood amenities. Second, the paper explores differences in the valuation of amenities by calculating prices in different urban areas. In more sparsely populated urban areas, distance to national parks becomes less important, but distance to primary roads becomes more important. Finally, housing and safety satisfaction represent the key components of life satisfaction.

Enforcement, Contract Design, and Default: Exploring the Financial Markets of Costa Rica

This paper examines the institutional determinants of incentives to repay in Costa Rica and their effects on defaults and the design of financial contracts. Enforcement mechanisms help to determine how much is paid back to creditors and how much shareholders receive as dividends. Theoretically, however, the most important effects will be on the observable characteristics of contracts, as rational agents foresee the incentives of other parties. As courts enforce contracts and punish defaulters, they determine the form contracts take and the magnitude and direction of investments. The paper contains findings on the practices of financial intermediaries that are discussed in the context of contract theory, with a focus on the formal financial intermediaries that are scattered throughout the country. Much of the information comes from primary sources, including a sample of almost 1,700 civil trials and a detailed survey on the credit policies of 31 intermediaries. This paper reviews the creditor-borrower relationship at all stages—ex ante, interim, and ex post. The evidence supports the importance of collateral and other ex post repayment incentives. The evidence also suggests that, contrary to the common view, banks are not passive lenders. They remain alert to how well projects perform and rely on previous experience and a rather sophisticated informational network in granting credit.

Bailouts in Costa Rica as a Result of Government Centralization and Discretionary Transfers

This paper investigates the inter-relation between the central government and the municipalities in Costa Rica. It examines episodes in which the central government has bailed out the local governments from their obligations. We employ empirical and descriptive methods to show how discretionary grants relate to the degree of fiscal discipline of the municipality to produce hidden bailouts. Political, demographic, and economic variables explain the allocation of these discretionary transfers. We illustrate the effects of the high concentration of decision-making of the central government on the fiscal performance of the municipalities. The municipalities play a limited role and its functioning largely depends upon the central government. We argue that the national administration would face a high political cost if it did not bail out the local government in several of the episodes studied. Using panel data from 1982-1997 on 81 cantones, we find that the fiscal effort of the local government is reduced by the presence of discretionary grants. The local governments finance local expenses with these discretionary transfers according to our empirical results. As expected from the centralization issue, political variables such as the affiliation of the local administration have significant effects on the resources received by the municipalities.

High Field de Haas - van Alphen Studies of the Fermi Surfaces of LaMIn5_{5} (M = Co, Rh, Ir)

We report measurements of the de Haas - van Alphen effect on a series of compounds, LaMIn$_{5}$ (M = Co, Rh, Ir). The results show that each of the Co and Ir Fermi surfaces (FSs) exhibit some portions that are two dimensional and some portions that are three dimensional. The most two dimensional character is exhibited in LaCoIn$_{5}$, less two dimensional behavior is seen in LaIrIn$_{5}$, no part of Fermi surface of LaRhIn$_{5}$ is found to have a two dimensional character. Thus the two dimensionality of portions of the FSs is largely determined by the d character of the energy bands while all of the effective masses remain $\leq$ 1.2. This fact has implications for the causes of the heavy fermion nature of superconductivity and magnetism in the Ce-based compounds having the similar composition and structure. All of the measurements were performed at the National High Magnetic Field Laboratory using either cantilever magnetometry or field modulation methods.Comment: 10 pages, 4 figure

What is the value of an observable between pre- and postselection?

Hall's recent derivation of an exact uncertainty relation [Phys. Rev. A64, 052103 (2001)] is revisited. It is found that the Bayes estimator of an observable between pre- and postselection equals the real part of the weak value. The quadratic loss function equals the expectation of the squared imaginary part of the weak value.Comment: 5 pages, accepted in Phys. Lett.

Assessing GEO and LEO Repeating Conjunctions Using High Fidelity Brute Force Monte Carlo Simulations

Probability of collision (P(sub c)) estimates for Earth-orbiting satellites typically assume a temporally-isolated conjunction event. However, under certain conditions two objects may experience multiple high-risk close approach events over the course of hours or days. In these repeating conjunction cases, the P(sub c) accumulates as each successive encounter occurs. The NASA Conjunction Assessment Risk Analysis team has updated its brute force Monte Carlo (BFMC) software to estimate such accumulating P(sub c) values for repeating conjunctions. This study describes the updated BFMC algorithm and discusses the implications for conjunction risk assessment

Intestinal Dysbiosis, the Tryptophan Pathway and Nonalcoholic Steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH), which may then progress to the development of cirrhosis and hepatocarcinoma. NASH is characterized by both steatosis and inflammation. Control of inflammation in NASH is a key step for the prevention of disease progression to severe sequalae. Intestinal dysbiosis has been recognized to be an important causal factor in the pathogenesis of NASH, involving both the accumulation of lipids and aggravation of inflammation. The effects of gut dysbiosis are mediated by adverse shifts of various intestinal commensal bacterial genera and their associated metabolites such as butyrate, tryptophan, and bile acids. In this review, we focus on the roles of tryptophan and its metabolites in NASH in association with intestinal dysbiosis and discuss possible therapeutic implications

Heisenberg-style bounds for arbitrary estimates of shift parameters including prior information

A rigorous lower bound is obtained for the average resolution of any estimate of a shift parameter, such as an optical phase shift or a spatial translation. The bound has the asymptotic form k_I/ where G is the generator of the shift (with an arbitrary discrete or continuous spectrum), and hence establishes a universally applicable bound of the same form as the usual Heisenberg limit. The scaling constant k_I depends on prior information about the shift parameter. For example, in phase sensing regimes, where the phase shift is confined to some small interval of length L, the relative resolution \delta\hat{\Phi}/L has the strict lower bound (2\pi e^3)^{-1/2}/, where m is the number of probes, each with generator G_1, and entangling joint measurements are permitted. Generalisations using other resource measures and including noise are briefly discussed. The results rely on the derivation of general entropic uncertainty relations for continuous observables, which are of interest in their own right.Comment: v2:new bound added for 'ignorance respecting estimates', some clarification