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A spectroscopic study of the peptide GCN4(107-125) seeks to test the hypothesis of Ptashne et al that acidicactivation domains form amphipatic alpha-helices to carry out their role of initiating DNA transcription. Circular dichroism, UV and NMR data show that GCN4(107-125) does not take on a stable secondary structure in aqueous solutionnor tend to form into an alpha-helix structure. The results, however, do not preclude a possible specific in vivo conformation in the presence of its targetprotein. Further experiments using the more active GCN4(107-144) are being undertaken.

We review a range of techniques related to navigation of unmanned vehicles through unknown environments with obstacles, especially those that rigorously ensure collision avoidance (given certain assumptions about the system). This topic continues to be an active area of research, and we highlight some directions in which available approaches may be improved. The paper discusses models of the sensors and vehicle kinematics, assumptions about the environment, and performance criteria. Methods applicable to stationary obstacles, moving obstacles and multiple vehicles scenarios are all reviewed. In preference to global approaches based on full knowledge of the environment, particular attention is given to reactive methods based on local sensory data, with a special focus on recently proposed navigation laws based on model predictive and sliding mode control. [ABSTRACT FROM PUBLISHER]

Abstract: The paper considers the problem of automatic path tracking by autonomous farming vehicles subject to wheel slips, which are characteristic for agricultural applications. Two guidance laws are proposed to solve this problem, and both explicitly take into account the constraints on the steering angle and ensure tracking an arbitrarily curved path. The first law is implemented by the pure sliding-mode controller, whereas the second one combines the sliding mode approach with a smooth nonlinear control law and requests control chattering at the reduced amplitude as compared with the first law. Mathematically rigorous proofs of global convergence and robust stability of the proposed guidance laws are presented. In doing so, the slipping effects are treated as bounded uncertainties. Simulation results and real world experiments confirm the applicability and performance of the proposed guidance approach. [Copyright &y& Elsevier]

Abstract: We consider the problem of reactively navigating an unmanned Dubins-like robot along an equidistant curve of an environmental object based on the distance to its boundary measured perpendicularly to the robot centerline and the angle of incidence of this perpendicular to the boundary. Such a situation holds if e.g., the measurements are supplied by range sensors rigidly mounted to the vehicle body at nearly right angles, or by a single sensor scanning a nearly perpendicular narrow sector. A sliding mode control law is proposed that drives the robot at a pre-specified distance from the boundary and maintains this distance afterwards. This is achieved without estimation of the boundary curvature and holds for boundaries with both convexities and concavities. Mathematically rigorous analysis of the proposed control law is provided, including an explicit account for the global geometry of the boundary. Computer simulations and experiments with real wheeled robots confirm the applicability and performance of the proposed guidance approach. [Copyright &y& Elsevier]

We determine the shortest (minimal in length) path on a unicycle-like mobile robot in a known environment with smooth (possibly non-convex) obstacles with a constraint on curvature of their boundaries. Furthermore, we propose a new reactive randomized algorithm of robot navigation in unknown environment and prove that the robot will avoid collisions and reach a steady target with probability 1. The performance of our algorithm is confirmed by computer simulations and outdoor experiments with a Pioneer P3-DX mobile wheeled robot. [ABSTRACT FROM AUTHOR]

Abstract: When employing autonomous wheeled robots, it is desirable to use navigation approaches that always prevent collisions. In this paper, we consider the problem of navigating multiple vehicles through an unknown static environment with limited sensing and communication capabilities available. We propose a decentralized, cooperative, reactive, model predictive control based collision avoidance scheme that plans short range paths in the currently sensed part of the environment, and show that it is able to prevent collisions from occurring. An auxiliary controller is employed to follow previously planned paths whenever the main path planning system fails to update the path. Simulations and real-world testing in various scenarios confirm the methods validity. [Copyright &y& Elsevier]

When employing autonomous helicopters, it is desirable to use navigation approaches, which firmly ensure safety. In this paper, we propose and compare two approaches to navigation through environments containing obstacles. The first uses sliding mode boundary following to maintain a prespecified distance to obstacles, and the second uses a model predictive control approach to plan short horizon trajectories around detected objects, while ensuring that the helicopter is brought to a halt within the sensor visibility radius. The navigation approaches are subjected to analysis for robustness, and simulations are carried out with a realistic helicopter model for verification. Additional real-world experiments were performed with a wheeled robot to demonstrate potential for real-time application. [ABSTRACT FROM PUBLISHER]

Recently there has been increased interest in developing methods for measuring poverty in a way that takes into account the lifetime experience of individuals. We analyze some specific proposals that take the so-called spells approach and consider how they differ in the manner in which they address issues of lifetime poverty, most notably the measurement of chronic poverty. Comparing these specific measures by applying them to a US panel data set, we provide important insights for further research in conceptualizing and measuring lifetime poverty. [ABSTRACT FROM AUTHOR]

An essay on whether insurance companies should be allowed to use the results of individual genetic tests for underwriting purposes is presented. It explains why restricting the use of genetic information would affect the insurance market through a phenomenon called adverse selection. It discusses how the type of adverse selection can offer arguments that are both in favor and against an outright ban on the use of genetic tests for pricing insurance.

Abstract: Females are more likely to attend Canadian universities and their participation rate has been increasing faster than that of males, generating a 15 percentage point gap by 2005. We investigate the determinants of attending university and explore the reasons for the increasing gender gap. As in the US literature, we find that conventional decompositions, averaging over the whole sample, attribute most of the gender gap to differences in variables, notably the University Premium. The average sample approach in these decompositions abstracts from the evolution over time of the participation rates by gender and from important detail at specific points in time, features that we try to overcome. We find that the rising level of the university participation rate for both women and men can be explained by changing societal norms, the dynamic influence of parental education, the University Premium, tuition fees and real income. The 2005 gap between the female and male participation rates can be accounted mostly (9 percentage points) by the gender differences in the University Premium and, to a lesser extent (6 percentage points), by differences in the coefficients in the female and male participation equations. [Copyright &y& Elsevier]

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Asymmetric information in the form of moral hazard and adverse selection can result in sizable program costs for government-provided crop insurance plans. We present a methodology and illustrative simulations to show how these two types of information problems interact in a way to create program costs for the providers of crop insurance. Our methodology allows us to ascertain the relative contributions to program costs of these two sources of asymmetric information. The exercise is useful in pointing out directions for future study seeking ways to improve the design of crop insurance plans. [ABSTRACT FROM AUTHOR]

We investigate whether regulations that ban insurance companies from access to individuals' genetic tests are likely to lead to substantial adverse selection costs for the specific example of the so-called breast cancer (BRCA1/2) genes. Using a data set including economic, demographic, and relevant family background information to simulate the market for 10-year term life insurance, we find generally only modest adverse selection costs associated with such a regulatory ban. However, for family background groups that are at high risk for carrying one of these genes, the efficiency cost of adverse selection may be significant should the test become widely adopted. [ABSTRACT FROM AUTHOR]